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 A023828 #10 Jun 13 2025 07:45:06
%S A023828 0,3,5,5,5,9,9,11,8,8,10,12,13,15,15,16,13,16,17,16,16,18,20,22,18,20,
%T A023828 21,20,20,22,24,25,24,25,26,26,24,28,28,29,24,28,29,29,28,29,32,34,31,
%U A023828 31,33,31,31,34,32,34,30,33,34,37,37,40,43,42,37,39,40,41,41,41,43,44,40,45,46,46,45,47
%N A023828 Sum of exponents in prime-power factorization of C(4n,n-2).
%H A023828 Ivan Neretin, <a href="/A023828/b023828.txt">Table of n, a(n) for n = 2..10000</a>
%F A023828 From _Amiram Eldar_, Jun 13 2025 (Start)
%F A023828 a(n) = A001222(A004332(n)).
%F A023828 a(n) = A023827(n) - A001222(3*n+2) + A001222(n-1). (End)
%t A023828 Join[{0}, Table[Total[FactorInteger[Binomial[4 n, n - 2]][[All, 2]]], {n, 3, 78}]] (* _Ivan Neretin_, Nov 02 2017 *)
%t A023828 a[n_] := PrimeOmega[Binomial[4*n, n-2]]; Array[a, 100, 2] (* _Amiram Eldar_, Jun 13 2025 *)
%o A023828 (PARI) a(n) = bigomega(binomial(4*n,n-2)); \\ _Amiram Eldar_, Jun 13 2025
%Y A023828 Cf. A001222, A004332, A023826, A023827, A023829, A023830, A023831, A023832, A023833, A023834, A023835, A023836.
%K A023828 nonn
%O A023828 2,2
%A A023828 _Clark Kimberling_
%E A023828 Offset corrected to 2 by _Ivan Neretin_, Nov 02 2017