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 A257771 #11 May 08 2015 11:59:49 %S A257771 1,2,5,8,11,13,31,37,53,61,73,79,97,122,127 %N A257771 Numbers n such that n*k - 1 and n*k + 1 are not both prime for any k < n. %C A257771 Numbers n such that A071558(n) > n. %o A257771 (PARI) is(n)=for(k=1,n-1,if(isprime(n*k-1)&&isprime(n*k+1), return(0))); 1 \\ _Charles R Greathouse IV_, May 08 2015 %o A257771 (PARI) is(n)=my(s=6/gcd(n,6)); forstep(k=s,n-1,s, if(isprime(n*k-1)&&isprime(n*k+1), return(0))); 1 \\ _Charles R Greathouse IV_, May 08 2015 %Y A257771 Cf. A071558, A220141. %K A257771 nonn,fini %O A257771 1,2 %A A257771 _Juri-Stepan Gerasimov_, May 07 2015