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 A300327 Poulet numbers (Fermat pseudoprimes to base 2) with a record number of divisors that are also Poulet numbers. 1
 341, 13981, 126217, 294409, 2113665, 4670029, 127479097, 140996401, 509033161, 8600780461, 42625846021, 220411358713, 2382784226641 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The number of divisors is 1, 2, 3, 4, 5, 6, 7, 8, 13, 15, 16, 20, 23, ... LINKS 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 Cf. A001567, A290497. Sequence in context: A210454 A069309 A086806 * A289305 A309285 A317556 Adjacent sequences:  A300324 A300325 A300326 * A300328 A300329 A300330 KEYWORD nonn,more AUTHOR Amiram Eldar, Mar 03 2018 STATUS approved

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Last modified September 29 17:14 EDT 2020. Contains 337432 sequences. (Running on oeis4.)