A358699 -id:A358699

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A358527

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

+0
3

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

(list; graph; refs; listen; history; text; internal format)

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.

KEYWORD

nonn

AUTHOR

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

EXTENSIONS

More terms from Amiram Eldar, Nov 23 2022

STATUS

approved

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