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 A274247 #9 Jun 29 2016 00:05:17 %S A274247 12348,16464,433664,444528,617400,790272,1053696,2534400,2737152, %T A274247 6585600,6667920,7024032 %N A274247 Numbers n such that n^k is the sum of a positive square and a positive cube for all k not divisible by 6. %C A274247 It is sufficient to prove that the decomposition exists for k=1..5, because if n^k = a^2+b^3, then n^(k+6) = (n^3*a)^2 + (n^2*b)^3. %e A274247 12348 is a term since 12348 = 98^2 + 14^3, 12348^2 = 9604^2 + 392^3, 12348^3 = 1361367^2 + 3087^3, 12348^4 = 76236552^2 + 259308^3, 12348^5 = 11206773144^2 + 5445468^3. %o A274247 (PARI) isA055394(n) = for(k=1, sqrtnint(n-1, 3), if(issquare(n-k^3), return(1)));0 %o A274247 isok(n) = isA055394(n) && isA055394(n^2) && isA055394(n^3) && isA055394(n^4) && isA055394(n^5) %Y A274247 Cf. A055394. %K A274247 nonn,more %O A274247 1,1 %A A274247 _Altug Alkan_, Jun 16 2016 %E A274247 a(6)-a(12) from _Giovanni Resta_, Jun 18 2016