A319165 Perfect powers whose prime indices are not relatively prime.

9, 25, 27, 49, 81, 121, 125, 169, 243, 289, 343, 361, 441, 529, 625, 729, 841, 961, 1331, 1369, 1521, 1681, 1849, 2187, 2197, 2209, 2401, 2809, 3125, 3249, 3481, 3721, 3969, 4225, 4489, 4913, 5041, 5329, 6241, 6561, 6859, 6889, 7569, 7921, 8281, 9261, 9409

Offset

1,1

Comments

A prime index of n is a number m such that prime(m) divides n.

Links

Table of n, a(n) for n=1..47.

Example

The sequence of integer partitions whose Heinz numbers are in the sequence begins: (22), (33), (222), (44), (2222), (55), (333), (66), (22222), (77), (444), (88), (4422), (99), (3333), (222222).

Mathematica

Select[Range[10000], With[{t=Transpose[FactorInteger[#]]}, And[GCD@@PrimePi/@t[[1]]>1, GCD@@t[[2]]>1]]&]

Crossrefs

Cf. A001597, A056239, A072774, A181819, A289509, A296150, A298748, A319151, A319161, A319163, A319164.

Sequence in context: A325373 A062739 A075109 * A319152 A244623 A339127

Adjacent sequences: A319162 A319163 A319164 * A319166 A319167 A319168

Keyword

nonn

Author

Gus Wiseman, Sep 12 2018

Status

approved