A125050 - OEIS

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A125050

a(1) = 1. If a(n) is composite, a(n+1) = 2*a(n)+1; otherwise, a(n+1) = 2*a(n).

2

1, 2, 4, 9, 19, 38, 77, 155, 311, 622, 1245, 2491, 4983, 9967, 19934, 39869, 79738, 159477, 318955, 637911, 1275823, 2551646, 5103293, 10206587, 20413175, 40826351, 81652702, 163305405, 326610811, 653221623, 1306443247, 2612886495

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OFFSET

1,2

LINKS

Table of n, a(n) for n=1..32.

FORMULA

a(n) = floor(c*2^n), where c = 0.6083600446... - Lorenzo Sauras Altuzarra, Jan 01 2023

MAPLE

a := proc(n)

local c, k:

c, k := 1, 1:

while c < n do

if k > 1 and not isprime(k) then k := 2*k+1: else k := 2*k: fi:

c := c+1: od:

k: end: # Lorenzo Sauras Altuzarra, Jan 02 2023

CROSSREFS

Sequence in context: A262864 A129784 A329356 * A056186 A265387 A293322

Adjacent sequences: A125047 A125048 A125049 * A125051 A125052 A125053

KEYWORD

nonn

AUTHOR

Franklin T. Adams-Watters, Nov 17 2006

STATUS

approved