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 A319051 #19 Sep 10 2018 07:58:06 %S A319051 47,97,241,349,547,773,1249,1447,1663,1847,1861,2347,2887,3049,3547, %T A319051 3607,3623,3697,4111,4373,4597,5237,5273,5749,6173,6857,7549,8467, %U A319051 8647,8719,9161,9349,9547,9749,11149,11321,11447,12049,12473,12689,12823,12941,13147,13291 %N A319051 Primes p such that none of p + 1, p + 2 and p + 3 are squarefree. %H A319051 Seiichi Manyama, <a href="/A319051/b319051.txt">Table of n, a(n) for n = 1..10000</a> %e A319051 48 = 2^4*3, 49 = 7^2 and 50 = 2*5^2. So 47 is a term. %e A319051 98 = 2*7^2, 99 = 3^2*11 and 100 = 2^2*5^2. So 97 is a term. %o A319051 (PARI) forprime(p=2, 1e5, if(!issquarefree(p+1) && !issquarefree(p+2) && !issquarefree(p+3), print1(p", "))) %Y A319051 Cf. A000040, A049098, A257108, A319049, A319050. %K A319051 nonn %O A319051 1,1 %A A319051 _Seiichi Manyama_, Sep 08 2018