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A320699
Numbers whose product of prime indices is a nonprime prime power (A246547).
2
7, 9, 14, 18, 19, 21, 23, 25, 27, 28, 36, 38, 42, 46, 49, 50, 53, 54, 56, 57, 63, 72, 76, 81, 84, 92, 97, 98, 100, 103, 106, 108, 112, 114, 115, 121, 125, 126, 131, 133, 144, 147, 152, 159, 162, 168, 171, 184, 189, 194, 196, 200, 206, 212, 216, 224, 227, 228
OFFSET
1,1
COMMENTS
First differs from A320325 at a(43) = 152, A320325(43) = 151.
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.
EXAMPLE
The sequence of all integer partitions whose Heinz numbers belong to the sequence begins: (4), (2,2), (4,1), (2,2,1), (8), (4,2), (9), (3,3), (2,2,2), (4,1,1), (2,2,1,1), (8,1), (4,2,1), (9,1), (4,4), (3,3,1), (16), (2,2,2,1), (4,1,1,1), (8,2), (4,2,2), (2,2,1,1,1), (8,1,1), (2,2,2,2), (4,2,1,1), (9,1,1), (25), (4,4,1), (3,3,1,1).
MATHEMATICA
Select[Range[100], With[{x=Times@@Cases[FactorInteger[#], {p_, k_}:>PrimePi[p]^k]}, !PrimeQ[x]&&PrimePowerQ[x]]&]
KEYWORD
nonn
AUTHOR
Gus Wiseman, Oct 19 2018
STATUS
approved