OFFSET
1,1
COMMENTS
The number of divisors is 1, 2, 3, 4, 5, 6, 7, 8, 13, 15, 16, 20, 23, ...
LINKS
Daniel Suteu, Table of n, a(n) for n = 1..25
Jan Feitsma and William F. Galway, Tables of pseudoprimes and related data.
R. G. E. Pinch, Pseudoprimes up to 10^13.
EXAMPLE
294409 is in the sequence since it is a Poulet number, and 4 of its divisors are also Poulet numbers (2701, 4033, 7957, 294409), more than for any smaller Poulet number.
PROG
(PARI) isP(n) = {Mod(2, n)^n==2 & !isprime(n) & n>1};
lista(nn) = {rec = 0; for (n=1, nn, if (isP(n), nb = sumdiv(n, d, isP(d)); if (nb > rec, print1(n, ", "); rec = nb); ); ); } \\ Michel Marcus, Mar 07 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Amiram Eldar, Mar 03 2018
EXTENSIONS
a(14)-a(20) from Daniel Suteu, Mar 06 2023
STATUS
approved