This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A359213 #24 Feb 01 2024 01:47:47 %S A359213 3,6,9,12,14,18,24,27,28,30,36,38,42,48,54,56,60,62,72,74,76,81,84,90, %T A359213 96,98,102,108,110,112,114,120,124,126,138,144,148,150,152,158,162, %U A359213 168,174,180,182,192,194,196,204,216,220,224,228,230,240,243,248,252 %N A359213 Numbers k such that rad(k) - 1 is prime. %H A359213 Amiram Eldar, <a href="/A359213/b359213.txt">Table of n, a(n) for n = 1..10000</a> %e A359213 rad(60) - 1 = 2*3*5 - 1 = 29, so 60 is a term. %t A359213 Select[Range[250], PrimeQ[Times @@ FactorInteger[#][[;; , 1]] - 1] &] (* _Amiram Eldar_, Dec 21 2022 *) %o A359213 (PARI) isok(k) = isprime(factorback(factor(k)[, 1]) - 1); \\ _Michel Marcus_, Dec 22 2022 %Y A359213 Cf. A007947, A097379. %K A359213 nonn %O A359213 1,1 %A A359213 _Arsen Vardanyan_, Dec 21 2022