OFFSET
1,2
COMMENTS
LINKS
Giovanni Resta, Table of n, a(n) for n = 1..58
MATHEMATICA
Select[Range[10^5], IntegerQ@ Sqrt[2 #^2 - DivisorSigma[1, #^2]] &] (* Michael De Vlieger, Jul 04 2017 *)
PROG
(PARI) isok(n) = issquare(2*n^2 - sigma(n^2)); \\ Michel Marcus, Jul 01 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Jens Voß, Jun 30 2017
EXTENSIONS
a(35)-a(38) from Giovanni Resta, Jul 27 2017
STATUS
approved