OFFSET
1,2
COMMENTS
The product of an even number of distinct members of A066436 is in the sequence. - Robert Israel, Aug 22 2017
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
60 is a term because psi(60) = 144 is a perfect square.
MAPLE
filter:= proc(n) issqr(n*mul(1+1/p, p=numtheory:-factorset(n))) end proc:
select(filter, [$1..1000]); # Robert Israel, Aug 22 2017
MATHEMATICA
Select[Range@ 750, IntegerQ@ Sqrt[# Sum[MoebiusMu[d]^2/d, {d, Divisors@ #}]] &] (* Michael De Vlieger, Aug 19 2017 *)
PROG
(PARI) a001615(n) = n*sumdivmult(n, d, issquarefree(d)/d);
is(n) = issquare(a001615(n));
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Altug Alkan, Aug 19 2017
STATUS
approved