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 A117003 #28 Jan 13 2025 01:37:31
%S A117003 1,4,6,10,10,18,14,24,21,30,22,44,26,42,40,52,34,66,38,70,56,66,46,
%T A117003 100,55,78,72,98,58,122,62,112,88,102,84,156,74,114,104,156,82,168,86,
%U A117003 154,138,138,94,216,105,170,136,182,106,216,132,212,152,174,118,294,122,186,186
%N A117003 a(n) = sigma(n) + A079667(n).
%D A117003 H. J. S. Smith, Report on the Theory of Numbers, reprinted in Vol. 1 of his Collected Math. Papers, Chelsea, NY, 1979, see p. 322.
%H A117003 Seiichi Manyama, <a href="/A117003/b117003.txt">Table of n, a(n) for n = 1..10000</a>
%F A117003 a(n) = Sum_{d|n} max(d, n/d). - _Seiichi Manyama_, Dec 27 2017
%F A117003 a(n) = Sum_{k in Z} H(4*n-k^2) where H() is the Hurwitz class number. - _Seiichi Manyama_, Jan 06 2018
%F A117003 G.f.: Sum_{n >= 1} x^(n^2)*(n + 2*x^n - n*x^(2*n))/(1 - x^n)^2 = x + 4*x^2 + 6*x^3 + 10*x^4 + 10*x^5 + .... Cf. A117004. - _Peter Bala_, Jan 19 2021
%F A117003 Sum_{k=1..n} a(k) ~ zeta(2) * n^2. - _Amiram Eldar_, Jan 12 2025
%t A117003 a[n_] := DivisorSum[n, Max[#, n/#] &]; Array[a, 100] (* _Amiram Eldar_, Jan 12 2025 *)
%o A117003 (PARI) {a(n) = sumdiv(n, d, max(d, n/d))} \\ _Seiichi Manyama_, Dec 27 2017
%Y A117003 Cf. A000203, A013661, A079667, A117004, A259825.
%K A117003 nonn,easy
%O A117003 1,2
%A A117003 _N. J. A. Sloane_, Apr 15 2006