A358527 Position of p in the factorization (without multiplicity) of 2^(p-1)-1, where p is the n-th odd prime.

1, 2, 2, 2, 4, 3, 3, 2, 3, 4, 6, 6, 3, 2, 3, 2, 8, 4, 5, 8, 3, 2, 5, 6, 6, 3, 2, 8, 6, 6, 4, 4, 4, 3, 5, 7, 5, 2, 3, 2, 14, 4, 7, 7, 8, 9, 3, 2, 5, 5, 4, 12, 4, 4, 2, 3, 8, 7, 12, 3, 3, 6, 4, 10, 3, 9, 13, 2, 7, 7, 2, 3, 5, 8, 2, 3, 13, 10, 10, 4, 19, 4, 13, 3

Offset

1,2

Links

Amiram Eldar, Table of n, a(n) for n = 1..196

Example

a(19) = 5 because the 19th odd prime is 71 and 71 is the 5th largest distinct prime factor of 2^(71-1)-1 = 1180591620717411303423 = 3 * 11 * 31 * 43 * 71 * 127 * 281 * 86171 * 122921.

Mathematica

Array[FirstPosition[FactorInteger[2^(# - 1) - 1], #][[1]] &[Prime[# + 1]] &, 50] (* Michael De Vlieger, Nov 27 2022 *)

Prog

(PARI) a(n) = my(p=prime(n+1), v=factor(2^(p-1)-1)[, 1]); vecsearch(v, p); \\ Michel Marcus, Nov 28 2022

Crossrefs

Cf. A065091, A098102, A358699.

Sequence in context: A194319 A208609 A249030 * A257126 A050493 A331851

Adjacent sequences: A358524 A358525 A358526 * A358528 A358529 A358530

Keyword

nonn

Author

G. L. Honaker, Jr., Nov 20 2022

Extensions

More terms from Amiram Eldar, Nov 23 2022

Status

approved