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A248822 Number of integers k^4 that divide 1!*2!*3!*...*n!. 5

%I

%S 1,1,1,2,3,8,10,36,64,200,432,630,1088,4800,7590,32448,47040,114240,

%T 164160,835920,1302840,4804800,7091712,25243920,39168000,171555840,

%U 320973840,667447200,1113944832,3338108928,5181926400,19372953600,31804416000,132562944000

%N Number of integers k^4 that divide 1!*2!*3!*...*n!.

%H Clark Kimberling and Alois P. Heinz, <a href="/A248822/b248822.txt">Table of n, a(n) for n = 1..1000</a> (first 400 terms from Clark Kimberling)

%e a(6) counts these integers k^4 that divide 24883200: 1^4, 2^4, 4^4, 8^4, 6^4, 12^4, 24^4.

%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), 4)+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 = 4; Table[t[m, n], {n, 1, z}] (* A248822 *)

%Y Cf. A000178, A056571, A248784, A248821, A248823.

%K nonn,easy

%O 1,4

%A _Clark Kimberling_, Oct 15 2014

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Last modified March 19 15:02 EDT 2019. Contains 321330 sequences. (Running on oeis4.)