cp's OEIS Frontend

A135434 a(n) is the smallest odd number that makes a(n)*2^N(n)-1 prime, where N(n) is the n-th Mersenne number that makes 2^N(n)-1 prime.

%I A135434 #14 Apr 03 2023 10:36:11
%S A135434 3,3,7,3,9,7,51,15,69,19,25,103,1905,273,139,13,4027,3619,2187,3211,
%T A135434 6621,1897,17461,2511,90579,30189,805,86539,30091,317917,198681,
%U A135434 755061,1283911,26869,1564347,4348099,383731,6020095
%N A135434 a(n) is the smallest odd number that makes a(n)*2^N(n)-1 prime, where N(n) is the n-th Mersenne number that makes 2^N(n)-1 prime.
%C A135434 First 22 terms are obtained by Mathematica. Terms from 23 to 38 are obtained by Jean Penna's LLR program.
%H A135434 Jean Penna, <a href="https://t5k.org/bios/page.php?id=431">LLR</a>.
%H A135434 Lei Zhou, <a href="https://t5k.org/bios/page.php?id=1273">Prime page</a>
%e A135434 First Mersenne number N(1)=2, 2^2-1=3 is the first Mersenne prime. 3*2^2-1=11 is prime;
%e A135434 Fifth Mersenne number N(5)=13, 2^13-1=8191 is the fifth Mersenne prime. 9*2^13-1=73727 is prime.
%Y A135434 Cf. A000043.
%K A135434 nonn,hard,more
%O A135434 1,1
%A A135434 _Lei Zhou_, Dec 13 2007
%E A135434 a(35)-a(37) from _Pierre CAMI_, Apr 06 2015
%E A135434 a(38) from _Lei Zhou_, Sep 04 2022