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 A171405 #11 Jul 09 2025 04:32:15
%S A171405 1,1,1,5,6,7,8,13,10,16,12,23,14,22,21,29,18,34,20,40,29,34,24,55,31,
%T A171405 40,37,54,30,67,32,61,45,52,48,86,38,58,53,88,42,91,44,82,75,70,48,
%U A171405 119,57,91,69,96,54,115,72,118,77,88,60,163,62,94,101,125,84,139,68,124,93,142
%N A171405 Sum of divisors of n, excluding divisors 2 and 3.
%F A171405 a(n) = A000203(n) - A178142(n). - _Amiram Eldar_, Aug 03 2024
%t A171405 a[n_] := DivisorSigma[1, n] - {0,2,3,2,0,5}[[Mod[n-1, 6] + 1]]; Array[a, 100] (* _Amiram Eldar_, Aug 03 2024 *)
%o A171405 (PARI) a(n) = sigma(n) - [0,2,3,2,0,5][(n-1) % 6 + 1]; \\ _Amiram Eldar_, Aug 03 2024
%Y A171405 Cf. A000203, A178142.
%K A171405 nonn
%O A171405 1,4
%A A171405 _Juri-Stepan Gerasimov_, Dec 07 2009, Apr 20 2010
%E A171405 Definition and some values corrected by _R. J. Mathar_, Jun 07 2010