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 A153788 #6 Aug 29 2016 00:17:51 %S A153788 0,0,1,1,3,7,11,7,15,15,23,31,47,71,191,95,191,255,575,511,767,767, %T A153788 1023,1151,1151,1727,1535,1535,4095,4095,5119,2047,6143,12287,12287, %U A153788 8191,12287,12287,24575,24575,36863,98303,131071,147455 %N A153788 Number of proper divisors of the Catalan number A000108(n). %H A153788 G. C. Greubel, <a href="/A153788/b153788.txt">Table of n, a(n) for n = 0..1000</a> %F A153788 a(n) = A032741(A000108(n)) = A152763(n) - 1. %t A153788 DivisorSigma[0, CatalanNumber@Range[0, 1000]] - 1 (* _G. C. Greubel_, Aug 28 2016 *) %o A153788 (PARI) a(n)=numdiv(binomial(2*n,n)/(n+1)) - 1 \\ _Charles R Greathouse IV_, Aug 29 2016 %Y A153788 Cf. A000108, A032741, A152762, A152763, A152988. %K A153788 nonn %O A153788 0,5 %A A153788 _Omar E. Pol_, Jan 18 2009