OFFSET
1,1
COMMENTS
Supersequence of perfect numbers (A000396).
a(14) > 10^12. - Giovanni Resta, Mar 01 2014
Up to a(13), note that the terms that are not perfect are deficient. - Michel Marcus, Mar 12 2014
EXAMPLE
Number 25 is a term because sigma(25) - 25 = 31 - 25 = 6 (perfect number).
PROG
(PARI) isok(n) = sigma(smn=sigma(n) - n) == 2*smn; \\ Michel Marcus, Mar 01 2014
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Jaroslav Krizek, Feb 28 2014
EXTENSIONS
a(10) from Michel Marcus, Mar 01 2014
a(11)-a(13) from Giovanni Resta, Mar 01 2014
STATUS
approved