OFFSET
1,1
COMMENTS
A prime index of n is a number m such that prime(m) divides n. The multiset of prime indices of n is row n of A112798.
Also numbers whose prime indices are all powers of a common prime number.
LINKS
EXAMPLE
The sequence of all integer partitions whose Heinz numbers belong to the sequence begins: (2), (3), (1,2), (4), (2,2), (1,3), (5), (1,1,2), (1,4), (7), (1,2,2), (8), (1,1,3), (2,4), (1,5), (9), (1,1,1,2), (3,3), (2,2,2), (1,1,4), (11), (1,7), (1,1,2,2), (1,8), (1,1,1,3), (13), (1,2,4), (1,1,5), (1,9), (1,1,1,1,2), (4,4), (1,3,3), (16), (1,2,2,2), (1,1,1,4), (2,8).
MATHEMATICA
Select[Range[100], PrimePowerQ[Times@@Cases[FactorInteger[#], {p_, k_}:>PrimePi[p]^k]]&]
PROG
(PARI) is(n) = my(f=factor(n)[, 1]~, p=1); for(k=1, #f, p=p*primepi(f[k])); isprimepower(p) \\ Felix Fröhlich, Oct 20 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Oct 19 2018
STATUS
approved