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 A283809 #14 Nov 21 2024 21:26:11 %S A283809 1,2,3,5,7,10,17,23,30,33,38,47,58,70,77,87,95,103,107,110,137,138, %T A283809 143,170,177,182,205,213,215,217,238,247,278,283,287,298,313,322,347, %U A283809 355,357,373,385,390,397,443,455,465,467,542,543,555,562,565,577,590,593,597,642,653,655,667,670,682 %N A283809 Squarefree numbers k such that 6*k - 1 and 6*k + 1 are twin primes. %H A283809 Charles R Greathouse IV, <a href="/A283809/b283809.txt">Table of n, a(n) for n = 1..10000</a> %t A283809 Select[Range[100], SquareFreeQ[#] && PrimeQ[6# - 1] && PrimeQ[6# + 1] &] (* _Indranil Ghosh_, Mar 17 2017 *) %o A283809 (Magma) [n: n in [1..700] | IsSquarefree(n) and IsPrime(6*n-1) and IsPrime(6*n+1)]; %o A283809 (PARI) is(n)=isprime(6*n-1) && isprime(6*n+1) && issquarefree(n) \\ _Charles R Greathouse IV_, Mar 17 2017 %Y A283809 Subsequence of A002822 and of A005117. Supersequence of A060212. %K A283809 nonn,easy %O A283809 1,2 %A A283809 _Juri-Stepan Gerasimov_, Mar 17 2017