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A046808 Recursive sequence of indices of Proth primes a*2^b + 1. 0
1, 2, 3, 5, 7, 14, 19, 46, 48, 62, 67, 74, 81, 89, 589, 2090, 2299, 7742 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Searched up to 7742*2^100000 + 1 (3871*2^100001 + 1 is the format in the Yves Gallot's Proth Program)

LINKS

Table of n, a(n) for n=0..17.

Y. Gallot, Proth.exe: Windows Program for Finding Large Primes

FORMULA

a(n) = least integer b greater than a(n-1) such that a(n-1)*2^b + 1 is prime

MATHEMATICA

t = {a = 1}; Do[If[PrimeQ[a*2^n + 1], AppendTo[t, a = n]], {n, 2, 2300}]; t (* Jayanta Basu, Jun 29 2013 *)

CROSSREFS

Sequence in context: A279953 A260523 A114625 * A097799 A005629 A028304

Adjacent sequences:  A046805 A046806 A046807 * A046809 A046810 A046811

KEYWORD

hard,nonn

AUTHOR

Chad Davis (cad16(AT)po.cwru.edu)

STATUS

approved

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Last modified October 16 17:06 EDT 2021. Contains 348042 sequences. (Running on oeis4.)