OFFSET
1,2
LINKS
Michael De Vlieger, Table of n, a(n) for n = 1..10000
EXAMPLE
128 has 8 divisors. Since 128 is a perfect power (128 = 2^7), and since 8 is also a perfect power (8 = 2^3), then 128 is in this sequence.
MATHEMATICA
Block[{nn = 10^4, s}, s = Union@ Flatten@ Table[n^e, {e, Prime@ Range@ PrimePi@ Log2@ nn}, {n, nn^(1/e)}]; Select[s, MemberQ[s, DivisorSigma[0, #]] &]] (* Michael De Vlieger, Nov 24 2017, after T. D. Noe at A001597 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Leroy Quet, Dec 08 2009
EXTENSIONS
Extended by Ray Chandler, Dec 10 2009
STATUS
approved