OFFSET
0,2
COMMENTS
a(221) <= 288230257234804736 = 2^(k-2)*(2^k-443) for k=30. - Michel Marcus, Apr 02 2020
a(221) > 10^13. - Giovanni Resta, Apr 12 2020
LINKS
Michel Marcus, Table of n, a(n) for n = 0..220
PROG
(PARI) g(n) = my(f=factor(n)); sigma(f) % eulerphi(f);
a(n) = {n *= 2; my(k=1); while (g(k) != n, k++); k; } \\ Michel Marcus, Mar 30 2020
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Marcus, Mar 30 2020
EXTENSIONS
a(0) prepended by Jinyuan Wang, Mar 30 2020
STATUS
approved