OFFSET
1,1
COMMENTS
PROG
(PARI) f(n) = if( n<2, n>0, my(A = divisors(n)); sum(k=1, #A-1, f(A[k])));
isok(n)={my(a=f(n)); a<n && f(a)==n; } \\ Michel Marcus, Sep 26 2018
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Amiram Eldar, Aug 22 2018
STATUS
approved