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 A161341 #21 Mar 15 2020 13:37:28 %S A161341 1,26,56,260,56,392,392,2192,56,392,392,2744,392,2744,2744,16952,56, %T A161341 392,392,2744,392,2744,2744,19208,392,2744,2744,19208,2744,19208, %U A161341 19208,125336,56,392,392,2744,392,2744,2744,19208,392,2744,2744,19208,2744,19208,19208 %N A161341 First differences of A161340. %F A161341 a(n) = A160429(n) for n>1 and n not a power of 2. %F A161341 a(n) = A160429(n) - 3n*(3n - 1) for n>1 and n a power of 2. %e A161341 From _Omar E. Pol_, Mar 15 2020: (Start) %e A161341 Written as an irregular triangle in which row lengths give A011782 the sequence begins: %e A161341 1; %e A161341 26; %e A161341 56, 260; %e A161341 56, 392, 392, 2192; %e A161341 56, 392, 392, 2744, 392, 2744, 2744, 16952; %e A161341 56, 392, 392, 2744, 392, 2744, 2744, 19208, 392, 2744, 2744, 19208, 2744, ... %e A161341 (End) %o A161341 (PARI) f(n) = 8*7^hammingweight(n-1); \\ A160429 %o A161341 ispow2(n) = my(k); (n==2) || (ispower(n,,&k) && (k==2)); %o A161341 a(n) = if (n==1, 1, if (ispow2(n), f(n) - 3*n*(3*n - 1), f(n))); \\ _Michel Marcus_, Mar 15 2020 %Y A161341 Cf. A011782, A160414, A161340, A161415. %K A161341 nonn,tabf %O A161341 1,2 %A A161341 _Omar E. Pol_, Jun 14 2009 %E A161341 Formula and more terms from _Nathaniel Johnston_, Nov 15 2010 %E A161341 More terms from _Jinyuan Wang_, Mar 14 2020