OFFSET
1,4096
COMMENTS
Perfect divisor of n is divisor d such that d^k = n for some k >= 1. See A175068 (product of perfect divisors of n), A175084 (possible values for product of perfect divisors of n) and A175085 (numbers m such that product of perfect divisors of x = m has no solution). a(n) = 0 or 1 for all n.
That is, this is the characteristic function of A175084. - Antti Karttunen, Nov 21 2017
LINKS
FORMULA
a(n) = Sum_{k=1..n} [A175068(k)==n]. - Antti Karttunen, Nov 21 2017
MATHEMATICA
With[{nn = 105}, ReplacePart[ConstantArray[0, nn], Flatten@ Table[{i -> 1}, {i, TakeWhile[#, # <= nn &] &@ Union@ Table[Apply[Times, Select[Divisors@ n, Or[# == 1, #^IntegerExponent[n, #] == n] &]], {n, nn}]}] ] ] (* Michael De Vlieger, Nov 21 2017 *)
PROG
(PARI)
A175068(n) = { my(m=1); fordiv(n, d, if((d>1)&&(d^valuation(n, d))==n, m*=d)); (m); };
CROSSREFS
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, Jan 24 2010
EXTENSIONS
More terms from Antti Karttunen, Nov 21 2017
STATUS
approved