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 A069061 #30 Mar 15 2025 14:03:59 %S A069061 4,6,13,18,48,84,176,258,800,1302,2736,4356,10928,20520,51792,65538, %T A069061 174768,351120,699056,1110276,3100240,5048232,11184816,17041416, %U A069061 49012992,82623888,211053040,284225796,727960800,1494039792,2863311536,4301668356,12611914848,20788904016 %N A069061 Sum of divisors of 2^n+1. %H A069061 Max Alekseyev, <a href="/A069061/b069061.txt">Table of n, a(n) for n = 1..1128</a> (terms 1..1062 from Amiram Eldar) %F A069061 a(n) = sigma(2^n+1). %F A069061 a(n) = A000203(A000051(n)). - _Michel Marcus_, Nov 24 2013 %t A069061 DivisorSigma[1, 2^Range[50] + 1] (* _Paolo Xausa_, Jul 05 2024 *) %o A069061 (PARI) a(n) = sigma(2^n+1); \\ _Michel Marcus_, Nov 24 2013 %Y A069061 Cf. A000051, A000203, A002185, A002587, A002589, A046798, A046799, A053285, A054992, A057957, A059886, A085029, A086257, A112092, A250291, A274906, A295501. %Y A069061 Row sums of A374237. %K A069061 nonn %O A069061 1,1 %A A069061 _Benoit Cloitre_, Apr 04 2002 %E A069061 More terms from _Amiram Eldar_, Oct 04 2019