1,2

sigma_4(n) is the sum of the 4th powers of the divisors of n (A001159).

sigma_{8j+4}(x)/phi[x] is an integer for j=0,..,500 for x=1,2,3,6,249,498 and supposed to hold for possible larger terms of A015762 and all j. Compare with comments to A015759, A091285, A015770. - Labos E. (labos(AT)ana.sote.hu), May 27 2004

Sequence in context: A018755 A018769 A015770 this_sequence A093038 A094469 A015766

Adjacent sequences: A015759 A015760 A015761 this_sequence A015763 A015764 A015765

nonn

Robert G. Wilson v (rgwv(AT)rgwv.com)