OFFSET
1,2
COMMENTS
Numbers whose exponents in their prime factorization are all congruent to 2 (mod 4).
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
FORMULA
MATHEMATICA
Select[Range[100], AllTrue[FactorInteger[#][[;; , 2]], OddQ] &]^2
PROG
(PARI) is(k) = issquare(k) && if(k == 1, 1, my(e = factor(k)[, 2]); for(i = 1, #e, if(e[i] % 4 != 2, return(0))); 1);
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Amiram Eldar, Jul 09 2024
STATUS
approved