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 A121612 #15 Oct 10 2024 08:17:47
%S A121612 2,3,4,8,10,12,16,20,22,117,408,432,444,492,504,508,1555,1560,1605,
%T A121612 1675,1790,5832,5940,5976,6048,6078,6102,6108,6132,6138,21175,21266,
%U A121612 21280,21301,21434,21462,21469,21616,21623,21749,21770,21784,81472,81528,81648
%N A121612 Numbers k such that the number of prime divisors of the k-th Catalan number (counted with multiplicity) divides k.
%C A121612 a(46) > 200000, if it exists. - _Amiram Eldar_, Oct 10 2024
%F A121612 {k such that A081399(k)|k} = {k such that A001222(A000108(k))|k}.
%e A121612 a(1) = 2 because bigomega(Catalan(2)) = bigomega(2) = 1 and 1 | 2.
%t A121612 fQ[n_] := Mod[n, Plus @@ (Last@# & /@ FactorInteger[ Binomial[2n, n]/(n + 1)])] == 0; s = {}; Do[ If[fQ@n, Print@n; AppendTo[s, n]], {n, 2, 35500}] (* _Robert G. Wilson v_, Sep 11 2006 *)
%Y A121612 Cf. A000108, A001222, A081399.
%K A121612 nonn
%O A121612 1,1
%A A121612 _Jonathan Vos Post_, Sep 08 2006
%E A121612 Corrected and extended (a(10)-a(42)) by _Robert G. Wilson v_, Sep 11 2006
%E A121612 a(43)-a(45) from _Amiram Eldar_, Oct 10 2024