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 A257568 #17 May 03 2015 11:04:14 %S A257568 3,2,13,5,59,751,1237,6053,10427,36671,1532579,351599,356989,12048691, %T A257568 105931211,96365273,190612867,18425983,1014695321,8763105101, %U A257568 20385719771,7508555437,97094976593,1911292838383,22999364895631,46158586887073,6373306898393 %N A257568 The least prime p such that the highest power of 3 that divides p^2 + 2 is n. %H A257568 Hiroaki Yamanouchi, <a href="/A257568/b257568.txt">Table of n, a(n) for n = 0..500</a> %e A257568 a(0) = 3 because 3^2+2=11 not divisible by 3, %e A257568 a(18) = 1014695321 because 1014695321^2+2 = 3^18*2657594587, %e A257568 a(21) = 7508555437 because 7508555437^2+2 = 3^21*17*317042521. %o A257568 (PARI) a(n)=if(n==1, return(2)); my(k=3^n,m=1,p); while(!issquare(m*k-2,&p) || !isprime(p), m+=2; if(m%3==0, m+=2)); p \\ _Charles R Greathouse IV_, May 01 2015 %Y A257568 Cf. A257567. %K A257568 nonn %O A257568 0,1 %A A257568 _Zak Seidov_, Apr 30 2015 %E A257568 a(16) corrected and a(22)-a(26) added by _Hiroaki Yamanouchi_, May 03 2015