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Revision History for A123340

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A123340

Least m such that 2^n+3^m is prime.
(history; published version)

#6 by Alois P. Heinz at Wed Feb 01 07:07:49 EST 2023

STATUS

reviewed

approved

#5 by Michel Marcus at Wed Feb 01 06:08:26 EST 2023

STATUS

proposed

reviewed

#4 by Jean-François Alcover at Wed Feb 01 05:00:43 EST 2023

STATUS

editing

proposed

#3 by Jean-François Alcover at Wed Feb 01 05:00:37 EST 2023

MATHEMATICA

a[n_] := Module[{m, t = 2^n}, For[m = 0, True, m++, If[PrimeQ[t + 3^m], Return[m]]]];

Table[a[n], {n, 0, 100}] (* Jean-François Alcover, Feb 01 2023 *)

STATUS

approved

editing

#2 by Russ Cox at Fri Mar 30 17:26:22 EDT 2012

AUTHOR

_Zak Seidov (zakseidov(AT)yahoo.com), _, Oct 11 2006

Discussion

Fri Mar 30

17:26

OEIS Server: https://oeis.org/edit/global/139

#1 by N. J. A. Sloane at Wed Dec 06 03:00:00 EST 2006

NAME

Least m such that 2^n+3^m is prime.

DATA

0, 0, 0, 1, 0, 2, 1, 1, 0, 2, 2, 4, 1, 3, 3, 1, 0, 8, 1, 4, 8, 8, 6, 2, 7, 27, 6, 13, 1, 10, 1, 6, 4, 8, 18, 9, 19, 2, 15, 29, 3, 3, 17, 10, 3, 11, 6, 2, 5, 20, 34, 4, 12, 10, 26, 1, 4, 2, 9, 29, 29, 10, 34, 13, 4, 8, 2, 1, 8, 10, 26, 50, 19, 12, 10, 8, 13, 27, 17, 9, 33, 4, 2, 17, 1, 7, 3, 5, 61, 26

OFFSET

0,6

EXAMPLE

a(0)=0 because 2^0+3^0=1+1=2 is prime,

a(3)=1 because 2^3+3^1=8+3=11 is prime,

a(17)=8 because 2^17+3^8=131072+6561=137633 is prime,

a(25)=27 because 33554432+7625597484987=7625631039419 is prime, etc.

KEYWORD

nonn

AUTHOR

Zak Seidov (zakseidov(AT)yahoo.com), Oct 11 2006

STATUS

approved