OFFSET
1,2
COMMENTS
EXAMPLE
The terms together with their prime indices begin:
1: {}
3: {2}
7: {4}
9: {2,2}
53: {16}
21: {2,4}
311: {64}
27: {2,2,2}
49: {4,4}
159: {2,16}
8161: {1024}
63: {2,2,4}
For example, the choices for a(12) = 63 are:
(1,1,1) (1,2,2) (2,1,4)
(1,1,2) (1,2,4) (2,2,1)
(1,1,4) (2,1,1) (2,2,2)
(1,2,1) (2,1,2) (2,2,4)
MATHEMATICA
primeMS[n_]:=If[n==1, {}, Flatten[Cases[FactorInteger[n], {p_, k_}:>Table[PrimePi[p], {k}]]]];
mnrm[s_]:=If[Min@@s==1, mnrm[DeleteCases[s-1, 0]]+1, 0];
az=Table[Times@@Length/@Divisors/@primeMS[n], {n, 1000}];
Table[Position[az, k][[1, 1]], {k, mnrm[az]}]
CROSSREFS
Positions of first appearances in A355731.
A000005 counts divisors.
A003963 multiplies together the prime indices of n.
A120383 lists numbers divisible by all of their prime indices.
A324850 lists numbers divisible by the product of their prime indices.
KEYWORD
nonn
AUTHOR
Gus Wiseman, Jul 21 2022
STATUS
approved