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 A081865 #19 Jan 08 2025 02:45:16
%S A081865 1,2188,78126,823544,4785157,19487172,62748518,170939688,410338674,
%T A081865 893871740,1801914272,3404825448,6103593751,10465138360,17249876310,
%U A081865 27512614112,42637932336,64340198544,94931877134,137293757384,194754273882,271818611108,373845175782
%N A081865 a(n) = sigma_7(2n-1).
%H A081865 Amiram Eldar, <a href="/A081865/b081865.txt">Table of n, a(n) for n = 1..10000</a>
%F A081865 Sum_{k=1..n} a(k) ~ c * n^8, where c = 17 * Pi^8 / 10080 = 16.00248... . - _Amiram Eldar_, Jan 07 2025
%t A081865 DivisorSigma[7, Range[1, 45, 2]] (* _Amiram Eldar_, Aug 17 2019 *)
%o A081865 (PARI) a(n) = sigma(2*n-1, 7); \\ _Michel Marcus_, Dec 04 2013
%Y A081865 Cf. A013955.
%K A081865 nonn
%O A081865 1,2
%A A081865 _Benoit Cloitre_, Apr 12 2003
%E A081865 Three more terms from _Michel Marcus_, Dec 04 2013