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 A023817 #19 Jun 12 2025 08:11:02
%S A023817 0,2,2,4,4,6,4,7,6,7,6,9,8,11,9,12,9,13,10,13,12,13,12,15,14,14,14,16,
%T A023817 14,17,12,18,16,16,15,18,15,18,17,20,19,22,20,22,22,23,20,25,21,24,22,
%U A023817 24,22,25,21,24,22,24,23,28,26,27,26,29,25,27,25,30,28,30,26,32,29,31,31,31,31,34,29,32
%N A023817 Sum of exponents in prime-power factorization of C(2n,n-1).
%H A023817 Ivan Neretin, <a href="/A023817/b023817.txt">Table of n, a(n) for n = 1..10000</a>
%F A023817 From _Amiram Eldar_, Jun 11 2025: (Start)
%F A023817 a(n) = A001222(A001791(n)).
%F A023817 a(n) = A023816(n) - A076191(n). (End)
%t A023817 Join[{0},Total[FactorInteger[#][[All,2]]]&/@Table[Binomial[2n,n-1], {n,2,80}]] (* _Harvey P. Dale_, Sep 14 2016 *)
%t A023817 Table[PrimeOmega[Binomial[2 n, n + 1]], {n, 1, 200}] (* _Clark Kimberling_, May 04 2025 *)
%o A023817 (PARI) a(n) = bigomega(binomial(2*n, n-1)); \\ _Amiram Eldar_, Jun 11 2025
%Y A023817 Cf. A001222, A001791, A023816, A023818, A076191.
%K A023817 nonn
%O A023817 1,2
%A A023817 _Clark Kimberling_