A318286 Number of strict multiset partitions of a multiset whose multiplicities are the prime indices of n.

1, 1, 1, 2, 2, 3, 2, 5, 5, 5, 3, 9, 4, 7, 9, 15, 5, 18, 6, 16, 14, 10, 8, 31, 17, 14, 40, 25, 10, 34, 12, 52, 21, 19, 27, 70, 15, 25, 31, 59, 18, 57, 22, 38, 80, 33, 27, 120, 46, 67, 44, 56, 32, 172, 42, 100, 61, 43, 38, 141, 46, 55, 143, 203, 64, 91, 54, 80

Offset: 1

Author

Gus Wiseman, Aug 23 2018

Keywords

• nonn

Links

• Andrew Howroyd, Table of n, a(n) for n = 1..500

Crossrefs

Cf. A001055, A007716, A045778, A181821, A305936, A316980, A317776.

Cf. A318283, A318284, A318285, A318287, A318360, A318361.

Programs

Mathematica

nrmptn[n_]:=Join@@MapIndexed[Table[#2[[1]],{#1}]&,If[n==1,{},Flatten[Cases[FactorInteger[n]//Reverse,{p_,k_}:>Table[PrimePi[p],{k}]]]]];
strfacs[n_]:=If[n<=1,{{}},Join@@Table[Map[Prepend[#,d]&,Select[strfacs[n/d],Min@@#>d&]],{d,Rest[Divisors[n]]}]];
Table[Length[strfacs[Times@@Prime/@nrmptn[n]]],{n,60}]

PARI

permcount(v) = {my(m=1, s=0, k=0, t); for(i=1, #v, t=v[i]; k=if(i>1&&t==v[i-1], k+1, 1); m*=t*k; s+=t); s!/m}
sig(n)={my(f=factor(n)); concat(vector(#f~, i, vector(f[i, 2], j, primepi(f[i, 1]))))}
count(sig)={my(r=0, A=O(x*x^vecmax(sig))); for(n=1, vecsum(sig)+1, my(s=0); forpart(p=n, my(q=1/prod(i=1, #p, 1 - x^p[i] + A)); s+=prod(i=1, #sig, polcoef(q, sig[i]))*(-1)^#p*permcount(p)); r+=(-1)^n*s/n!); r/2}
a(n)={if(n==1, 1, count(sig(n)))} \\ Andrew Howroyd, Dec 18 2018

Formula

a(n) = A045778(A181821(n)).

a(prime(n)^k) = A219585(n, k). - Andrew Howroyd, Dec 17 2018