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I can't stop thinking about Papua New Guinea

https://notnottalmud.substack.com/p/why-i-cant-stop-thinking-about-papua
451•networked•6h ago•176 comments

CSS-Tricks in Limbo

https://vale.rocks/micros/20260915-0135
103•edent•5h ago•25 comments

Suspected sabotage causes major Netherlands rail disruption

https://www.bbc.com/news/articles/c8ly49w9g1edo
236•choult•2h ago•217 comments

Show HN: An e-ink frame that hears birds and draws them as 1800s illustrations

https://github.com/arnegiacomo/fugleramme
6•arnemunthekaas•37m ago•0 comments

25 Years of Mass Surveillance Is Enough

https://www.schneier.com/blog/archives/2026/09/25-years-of-mass-surveillance-is-enough.html
88•iamnothere•1h ago•7 comments

Alternatives to MinIO for single-node local S3

https://rmoff.net/2026/01/14/alternatives-to-minio-for-single-node-local-s3/
91•rmoff•4h ago•49 comments

iOS 27, iPadOS 27, and macOS 27

https://www.apple.com/newsroom/2026/09/major-updates-for-apples-software-platforms-are-now-availa...
656•throw0101d•19h ago•754 comments

OpenArm: An open-source 7DOF humanoid arm

https://github.com/enactic/OpenArm
138•Lwrless•1d ago•25 comments

The k-server conjecture is true

https://arxiv.org/abs/2609.15979
45•iamsyr•5h ago•18 comments

OpenAI buys smartphone camera maker Glass Imaging for $300M

https://techcrunch.com/2026/09/14/openai-buys-smartphone-camera-maker-glass-imaging-for-300-milli...
24•myth_drannon•1h ago•6 comments

A rough guide for going back to the Moon

https://research.ibm.com/blog/nasa-ibm-lunar-foundation-model
21•gmays•22h ago•10 comments

4,400-Year-Old Tomb of Egyptian Judge Found at Saqqara with Colors on Walls

https://arkeonews.net/4400-year-old-tomb-of-an-egyptian-judge-found-at-saqqara-with-colors-still-...
174•arunbahl•2d ago•53 comments

Pion, an agent designed to run any company autonomously

https://andonlabs.com/blog/why-we-built-pion
436•lukaspetersson•19h ago•538 comments

US confirms for first time it has deployed space weapons

https://www.bbc.com/news/articles/ck790xg41ygro
113•harporoeder•9h ago•70 comments

When Google Cuts Off Access: Poland and the World

https://dossier.reasoner.pl/artykul/
9•marekfocus•1h ago•1 comments

Linux from Scratch

https://www.linuxfromscratch.org/
256•sippingabonedry•8h ago•79 comments

There are only twelve 4x4 sudokus (and a cool trick for finding minimal subsets)

https://baldino.dev/blog/there-are-only-twelve-4x4-sudokus/
15•Fran314•1d ago•7 comments

Lingo.dev (YC F24) is hiring a senior content engineer (Remote, worldwide)

https://lingo.dev/en/careers/ff88132a-cb79-4d35-a6a0-a6230de7a013
1•maxpr•6h ago

XCancel service is suspended until further notice

https://xcancel.com/#
695•gaganyaan•1d ago•968 comments

Charts built for Chat

https://dbtcharts.com/blog/charts-built-for-chat/
263•thingsilearned•15h ago•78 comments

OpenAI bots knew about the RubyGems caching vulnerability

https://tenderlovemaking.com/2026/09/11/what-a-time-to-be-alive/
486•gregnavis•1d ago•392 comments

Show HN: Redis City – Explore how Redis works in an interactive 3D model

https://poltora.dev/redis
127•poltora•2d ago•22 comments

Dropping eBPF CPU Cost by About 90% with Memoization (Not AI Gen)

https://nathannaveen.dev/posts/dropping-ebpf-cpu-cost-by-90/
136•nathannaveen•22h ago•29 comments

A beginning for mathematics

https://www.daniellitt.com/blog/2026/9/13/a-beginning-for-mathematics/
250•robinhouston•21h ago•128 comments

Inverse-Square Law

https://blog.coredump.cx/p/inverse-square-law
3•surprisetalk•1d ago•0 comments

Distributed Systems Classics (2017)

https://nvartolomei.com/dist-sys-classics/
323•grep_it•21h ago•68 comments

25 Years of Mass Surveillance Is Enough [Auth: Cindy Cohn; Bruce Schneier]

https://www.lawfaremedia.org/article/25-years-of-mass-surveillance-is-enough
12•mdp2021•1h ago•2 comments

Compressing a flag to 11 bits

https://read.vantezzen.io/miniflags
172•bennett_dev•2d ago•65 comments

Forgotten Woodlands

https://storymaps.arcgis.com/stories/9b790daf22ba4e87836f467abb1c7e49
80•NaOH•3d ago•26 comments

Ubuntu 26.10 completes transition to Rust-based coreutils

https://www.omgubuntu.co.uk/2026/09/ubuntu-2610-rust-coreutils-complete
233•theanonymousone•23h ago•250 comments
Open in hackernews

Right-Truncatable Prime Counter

https://github.com/EbodShojaei/Right-Truncatable-Primes
9•rainmans•1y ago

Comments

throwawaymaths•1y ago
Curious about base 2. Obviously if you hit a 0 it's immediately not prime, but maybe adjust the rules so:

- you drill through as many 0's on the right.

- you finish on 1.

3, 5, 7, 11, 13, 15, 17 are all right truncatable, 19 is the first non-truncatable prime in this scheme.

nh23423fefe•1y ago
i dont think smaller radixes make the problem more interesting. the problem is interesting because base 10 has a large branching factor
throwawaymaths•1y ago
I think in the base2 reformulation I propose we do not know for certain if the list of numbers terminates, as all Fermat primes are in the set and we don't know if there are infinitely many Fermat primes.

For base-10 and the original rules the set is provably closed.

"Drilling through zeros" makes the branching unbounded.

jinwoo68•1y ago
There's a Project Euler problem for finding truncatable prime numbers, from both left and right: https://projecteuler.net/problem=37
thechao•1y ago
Just in case any else is wondering: there are only 83 right-truncatable primes (RTP) and that is it. There's two constraints that let you see this "immediately":

1. An RTP must start with {2,3,5,7,9}; and,

2. An RTP must end with {1,3,7,9}.

So, let's take the largest RTP (73939133) and try to "extend" it: there are only four possible extensions: 73939133[1], 73939133[3], 73939133[7], 73939133[9]. None of these are prime. This holds for the other 8-digit RTPs. Therefore, there is no extension to a 9-or-longer RTP. Thus, the list is exhaustive.