A248823 - OEIS

%I #11 Oct 27 2023 20:44:53

%S 1,1,1,2,2,6,8,10,42,64,200,432,588,1024,3888,6300,21120,33696,52080,

%T 114240,328320,816480,3326400,4435200,6469632,20616960,57153600,

%U 145411200,258003900,320973840,791513856,1634592960,6403719168,9967104000,34939296000

%N Number of integers k^5 that divide 1!*2!*3!*...*n!.

%H Alois P. Heinz, <a href="/A248823/b248823.txt">Table of n, a(n) for n = 1..1000</a> (first 400 terms from Clark Kimberling)

%e a(6) counts these integers k^5 that divide 24883200:  1, 32, 1024, 7776, 32768, 248832, these being k^5 for k = 1, 2, 3, 4, 6, 12.

%p b:= proc(n) option remember; add(i[2]*x^numtheory[pi](i[1]),

%p       i=ifactors(n)[2])+`if`(n=1, 0, b(n-1))

%p     end:

%p c:= proc(n) option remember; b(n)+`if`(n=1, 0, c(n-1)) end:

%p a:= n->(p->mul(iquo(coeff(p, x, i), 5)+1, i=1..degree(p)))(c(n)):

%p seq(a(n), n=1..30);  # _Alois P. Heinz_, Oct 16 2014

%t z = 40; p[n_] := Product[k!, {k, 1, n}];

%t f[n_] := f[n] = FactorInteger[p[n]];

%t r[m_, x_] := r[m, x] = m*Floor[x/m]

%t u[n_] := Table[f[n][[i, 1]], {i, 1, Length[f[n]]}];

%t v[n_] := Table[f[n][[i, 2]], {i, 1, Length[f[n]]}];

%t t[m_, n_] := Apply[Times, 1 + r[m, v[n]]/m]

%t m = 5; Table[t[m, n], {n, 1, z}] (* A248823 *)

%Y Cf. A000178, A248784, A248821, A248822.

%K nonn,easy

%O 1,4

%A _Clark Kimberling_, Oct 15 2014