OFFSET

1,1

COMMENTS

a(6..11) = { 46475520, 48933360, 50995620, ..., 72807696 } are the first terms not in A027687 (4-perfect numbers), which is obviously a subsequence.

a(11..12) = { 72807696, 142990848 } are the first terms that are not multiples of 60.

LINKS

Eric Weisstein's World of Mathematics, Sociable Numbers

PROG

(PARI) is_A355279(n, f(x)=if(x && x%4==0, sigma(x\4)))= f(f(sigma(n)))==n*4

CROSSREFS

KEYWORD

nonn,more

AUTHOR

M. F. Hasler, Sep 25 2022

STATUS

approved