OFFSET
1,1
COMMENTS
Essentially the same as A087797. - Ilya Gutkovskiy, Dec 26 2016
EXAMPLE
a(1) = 2 because sigma_3(2) = 1^3 + 2^3 = 9 and 9 == 1 (mod 2);
a(2) = 3 because sigma_3(3) = 1^3 + 3^3 = 28 and 28 == 1 (mod 3);
a(3) = 4 because sigma_3(4) = 1^3 + 2^3 + 4^3 = 73 and 73 == 1 (mod 4), etc.
MATHEMATICA
Select[Range[300], Mod[DivisorSigma[3, #1], #1] == 1 & ]
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Ilya Gutkovskiy, Oct 04 2016
EXTENSIONS
Edited by Ilya Gutkovskiy, Dec 26 2016
STATUS
approved