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 A271225 #8 Apr 09 2016 13:04:07 %S A271225 2,1,2,18,6,2,354,118,1107,369,123,41,239803,495074,3475362,1158454, %T A271225 7887171,2629057,56207062,246253281,82084427,5389722857,25755119139, %U A271225 8585039713,53195580742,193589999521 %N A271225 a(n) = (A268924(n)^2 + 2)/3^n, n >= 0. %C A271225 a(n) is an integer because b(n) = A268924(n) satisfies b(n)^2 + 2 == 0 (mod 3^n), n >= 0. %C A271225 See A268924 for details, links and references. %F A271225 a(n) = (b(n)^2 + 2)/3^n, n >= 0, with b(n) = A268924(n). %e A271225 a(0) = (0^2 + 2)/1 = 2. %e A271225 a(4) = (22^2 + 2)/3^4 = 6. %o A271225 (PARI) b(n) = 3^n - truncate(sqrt(-2+O(3^(n)))); %o A271225 a(n) = (b(n)^2 + 2)/3^n; \\ _Michel Marcus_, Apr 09 2016 %Y A271225 Cf. A268924, A271223, A271226 (companion sequence). %K A271225 nonn,easy %O A271225 0,1 %A A271225 _Wolfdieter Lang_, Apr 05 2016