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 A224880 #40 Mar 17 2024 03:10:04
%S A224880 3,7,10,15,16,24,22,31,31,38,34,52,40,52,54,63,52,75,58,82,74,80,70,
%T A224880 108,81,94,94,112,88,132,94,127,114,122,118,163,112,136,134,170,124,
%U A224880 180,130,172,168,164,142,220,155,193,174,202,160,228,182,232,194,206
%N A224880 a(n) = 2n + sum of divisors of n.
%C A224880 This sequence is A033880 for the negative integers, thus making explicit the mapping noted in A075701.
%C A224880 From _Omar E. Pol_, Jun 21 2018: (Start)
%C A224880 a(n) is also the total area of the terraces and the vertical sides that are visible in the perspective view at the n-th level (starting from the top) of the stepped pyramid described in A245092.
%C A224880 Partial sums give A299692. (End)
%H A224880 T. D. Noe, <a href="/A224880/b224880.txt">Table of n, a(n) for n = 1..10000</a>
%F A224880 a(n) = A155085(n) + n.
%F A224880 a(n) = 2n + sigma(n) = A005843(n) + A000203(n) = A033879(n) + 2*A000203(n) = A033880(n) + 2*A005843(n) = 2*A155085(n) - A000203(n) = 2*A000203(n) - A033880(n). - _Wesley Ivan Hurt_, Jul 24 2013
%F A224880 G.f.: 2*x/(1 - x)^2 + Sum_{k>=1} x^k/(1 - x^k)^2. - _Ilya Gutkovskiy_, Mar 17 2017
%F A224880 a(n) = A001065(n) + A008585(n). - _Omar E. Pol_, Mar 06 2018
%F A224880 Sum_{k=1..n} a(k) = c * n^2 + O(n*log(n)), where c = zeta(2)/2 + 1 = A072691 + 1 = 1.822467... . - _Amiram Eldar_, Mar 17 2024
%e A224880 a(6) = 2*6 + (1+2+3+6) = 24.
%p A224880 with(numtheory); seq(2*k+sigma(k),k=1..100); # _Wesley Ivan Hurt_, Jul 24 2013
%t A224880 Table[2*n+DivisorSigma[1,n],{n,64}]
%o A224880 (PARI) vector(80, n, 2*n + sigma(n)) \\ _Michel Marcus_, Aug 19 2015
%Y A224880 Cf. A000203, A033879, A033880, A072691, A075701, A155085, A237593, A245092, A299692.
%K A224880 nonn
%O A224880 1,1
%A A224880 _Hans Havermann_, Jul 23 2013