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 A023822 #11 Jun 12 2025 08:11:56
%S A023822 0,3,3,6,5,7,7,10,9,10,9,12,9,12,12,14,13,15,12,19,15,17,17,18,18,20,
%T A023822 19,20,16,21,20,23,20,21,20,23,18,23,21,25,26,27,27,30,27,28,28,31,27,
%U A023822 31,27,33,31,33,31,32,31,33,31,34,30,36,34,34,31,33,31,37,32,35,34,37,36,37,37,39,35,37
%N A023822 Sum of exponents in prime-power factorization of C(3n,n-3).
%H A023822 Ivan Neretin, <a href="/A023822/b023822.txt">Table of n, a(n) for n = 3..10000</a>
%F A023822 From _Amiram Eldar_, Jun 12 2025: (Start)
%F A023822 a(n) = A001222(A004321(n)).
%F A023822 a(n) = A023821(n) - A001222(2*n+3) + A001222(n-2). (End)
%t A023822 Join[{0}, Table[Total[FactorInteger[Binomial[3 n, n - 3]][[All, 2]]], {n, 4, 80}]] (* _Ivan Neretin_, Nov 02 2017 *)
%t A023822 a[n_] := PrimeOmega[Binomial[3*n, n-3]]; Array[a, 100, 3] (* _Amiram Eldar_, Jun 12 2025 *)
%o A023822 (PARI) a(n) = bigomega(binomial(3*n, n-3)); \\ _Amiram Eldar_, Jun 12 2025
%Y A023822 Cf. A001222, A004321, A023819, A023820, A023822, A023823, A023824, A023825.
%K A023822 nonn
%O A023822 3,2
%A A023822 _Clark Kimberling_
%E A023822 Offset corrected to 3 by _Ivan Neretin_, Nov 02 2017