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A078683 Least prime of the form n*2^m+1 for m>0, or 0 if there is no such prime. 2

%I #21 Mar 13 2023 07:19:36

%S 3,5,7,17,11,13,29,17,19,41,23,97,53,29,31,257,137,37,1217,41,43,89,

%T 47,97,101,53,109,113,59,61,7937,257,67,137,71,73,149,1217,79,641,83,

%U 337,173,89,181,11777

%N Least prime of the form n*2^m+1 for m>0, or 0 if there is no such prime.

%C The next prime has 178 digits. See A078680 for the values of m.

%H Vincenzo Librandi, <a href="/A078683/b078683.txt">Table of n, a(n) for n = 1..1000</a>

%t Table[m=1; While[! PrimeQ[p = n*2^m + 1], m++]; p, {n, 50}]

%o (PARI) a(n)=if(n<0, 0, m=1; while(isprime(n*2^m+1)==0, m++); n*2^m+1)

%Y Cf. A078680.

%K nonn

%O 1,1

%A _Benoit Cloitre_, Dec 17 2002

%E Edited by _T. D. Noe_, Feb 25 2011

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Last modified March 28 12:26 EDT 2024. Contains 371254 sequences. (Running on oeis4.)