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 A152981 #13 Nov 26 2019 04:18:52
%S A152981 1,1,3,7,13,32,72,128,360,1008,3836,9408,15512,66960,252720,785148,
%T A152981 1137960,3340800,13072776,42465024,69530400,238761600,678562560,
%U A152981 2412043920,5270534880,10943277120,44922182340,117229255200,209990825568,623486730240,1698651339840,7019676332760,18578092462280
%N A152981 Sum of divisors of Motzkin number A001006(n).
%H A152981 Amiram Eldar, <a href="/A152981/b152981.txt">Table of n, a(n) for n = 0..200</a>
%F A152981 a(n) = sigma(A001006(n)) = A000203(A001006(n)).
%p A152981 A152981 := proc(n) numtheory[sigma](A001006(n)) ; end proc:
%p A152981 seq(A152981(n),n=0..40) ; # _R. J. Mathar_, Jul 08 2011
%t A152981 mot[0] = 1; mot[n_] := mot[n] = mot[n - 1] + Sum[mot[k] * mot[n - 2 - k], {k, 0, n - 2}]; Table[DivisorSigma[1, mot[n]], {n, 0, 32}] (* _Amiram Eldar_, Nov 26 2019 *)
%Y A152981 Cf. A000005, A000203, A001006, A152761.
%K A152981 nonn
%O A152981 0,3
%A A152981 _Omar E. Pol_, Dec 20 2008