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 A023818 #12 Jun 12 2025 08:10:33
%S A023818 0,2,3,5,4,4,6,8,6,7,8,9,8,10,11,12,11,11,12,14,11,12,14,15,13,15,16,
%T A023818 16,13,13,17,19,14,16,18,17,15,18,19,22,20,20,21,24,21,20,23,24,23,24,
%U A023818 22,23,22,23,24,25,22,24,27,27,22,26,29,30,26,26,28,30,27,28,31,31,29,31,31,33,31,28,31
%N A023818 Sum of exponents in prime-power factorization of C(2n,n-2).
%H A023818 Ivan Neretin, <a href="/A023818/b023818.txt">Table of n, a(n) for n = 2..10000</a>
%F A023818 From _Amiram Eldar_, Jun 12 2025: (Start)
%F A023818 a(n) = A001222(A002694(n)).
%F A023818 a(n) = A023817(n) - A022559(n+2) + A022559(n-1). (End)
%t A023818 Join[{0}, Table[Total[FactorInteger[Binomial[2 n, n - 2]][[All, 2]]], {n, 3, 80}]] (* _Ivan Neretin_, Nov 02 2017 *)
%t A023818 a[n_] := PrimeOmega[Binomial[2*n, n-2]]; Array[a, 100, 2] (* _Amiram Eldar_, Jun 12 2025 *)
%o A023818 (PARI) a(n) = bigomega(binomial(2*n, n-2)); \\ _Amiram Eldar_, Jun 12 2025
%Y A023818 Cf. A001222, A002694, A023816, A023817.
%K A023818 nonn
%O A023818 2,2
%A A023818 _Clark Kimberling_
%E A023818 Offset corrected to 2 by _Ivan Neretin_, Nov 02 2017