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 A152988 #14 Dec 01 2019 07:15:51
%S A152988 0,0,0,0,7,47,193,236,1579,4195,18461,62143,275781,1131909,7434169,
%T A152988 10522660,72469339,268486155,1442237845,4284330539,18146555293,
%U A152988 62021099893,248289236937,798007352239,2832660377605,11922780595861
%N A152988 Sum of proper divisors minus the number of proper divisors of Catalan number A000108(n).
%H A152988 Amiram Eldar, <a href="/A152988/b152988.txt">Table of n, a(n) for n = 0..1667</a>
%F A152988 a(n) = A001065(A000108(n)) - A032741(A000108(n)) = A152770(A000108(n)).
%e A152988 a(5)=47 because A000108(5)=42 has 7 proper divisors: 1,2,3,6,7,14,21 and 1+2+3+6+7+14+21-7 = 47. - _Emeric Deutsch_, Dec 31 2008
%p A152988 with(numtheory): seq(sigma(binomial(2*n, n)/(n+1))-binomial(2*n, n)/(n+1)-tau(binomial(2*n, n)/(n+1))+1, n = 1 .. 27); # _Emeric Deutsch_, Dec 31 2008
%t A152988 diff[n_] := DivisorSigma[1, n] - DivisorSigma[0, n] - n + 1; Table[diff[ CatalanNumber[n] ], {n, 0, 25}] (* _Amiram Eldar_, Dec 01 2019 *)
%Y A152988 Cf. A000005, A000108, A000203, A001065, A032741, A152770.
%K A152988 nonn
%O A152988 0,5
%A A152988 _Omar E. Pol_, Dec 20 2008, Jan 07 2009
%E A152988 Extended by _Emeric Deutsch_, Dec 31 2008