OFFSET
1,1
COMMENTS
Seems to contain all numbers of form k^2*p^2 where p are primes in A002476, k is not congruent to p and >=1.
Squares in A067051. - Michel Marcus, Dec 26 2013
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
FORMULA
Conjecture: a(n) = A072864(n)^2. - R. J. Mathar, May 19 2020
MAPLE
with(numtheory); A074216:=n->`if`(1-ceil(sigma(n^2)/3)+floor(sigma(n^2)/3)=1, n^2, NULL); seq(A074216(n), n=1..200); # Wesley Ivan Hurt, Dec 06 2013
MATHEMATICA
Select[Range[150]^2, Divisible[DivisorSigma[1, #], 3]&] (* Harvey P. Dale, Jul 10 2012 *)
PROG
(PARI) isok(n) = issquare(n) && !(sigma(n) % 3); \\ Michel Marcus, Aug 17 2019
(Magma) [n: n in [1..14161]|IsSquare(n) and DivisorSigma(1, n) mod 3 eq 0 ]; // Marius A. Burtea, Aug 17 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
Benoit Cloitre, Sep 17 2002
STATUS
approved