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 A152761 #20 Feb 10 2025 04:39:48
%S A152761 1,1,3,6,24,96,336,672,3024,9072,35280,120960,483840,1874880,10108800,
%T A152761 20217600,107827200,398131200,1919877120,6051594240,24710676480,
%U A152761 86487367680,339771801600,1141066967040,4122564526080,16784726999040
%N A152761 Sum of divisors of Catalan number A000108(n).
%H A152761 Amiram Eldar, <a href="/A152761/b152761.txt">Table of n, a(n) for n = 0..1667</a>
%H A152761 Volkan Yildiz, <a href="https://arxiv.org/abs/2502.04619">Notes on Divisibility of Catalan Numbers</a>, arXiv:2502.04619 [math.CO], 2025.
%F A152761 a(n) = sigma(A000108(n)) = A000203(A000108(n)).
%F A152761 a(n) = A152762(n) + A000108(n). - _R. J. Mathar_, Jan 08 2009
%p A152761 with(numtheory): seq(sigma(binomial(2*n, n)/(n+1)), n = 0 .. 25); # _Emeric Deutsch_, Jan 10 2009
%p A152761 A000108 := proc(n) binomial(2*n,n)/(n+1) ; end: A000203 := proc(n) numtheory[sigma](n) ; end: A152761 := proc(n) A000203(A000108(n)) ; end: for n from 0 to 30 do printf("%d,",A152761(n)) ; od: # _R. J. Mathar_, Jan 08 2009
%t A152761 DivisorSigma[1,CatalanNumber[Range[0,30]]] (* _Harvey P. Dale_, Apr 17 2015 *)
%o A152761 (PARI) a(n) = sigma(binomial(2*n,n)/(n+1)); \\ _Michel Marcus_, Feb 09 2025
%Y A152761 Cf. A000108, A000203, A152762.
%K A152761 easy,nonn
%O A152761 0,3
%A A152761 _Omar E. Pol_, Dec 14 2008
%E A152761 Extended by _R. J. Mathar_ and _Emeric Deutsch_, Jan 08 2009