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A129786
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Least k such that 2^(2^n)+k is prime.
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2
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0, 1, 1, 1, 1, 15, 13, 51, 297, 75, 643, 981, 1761, 897, 2775, 118113, 44061, 5851
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OFFSET
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0,6
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COMMENTS
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It is conjectured that a(n)>=3 for n>=5.
For n>11, 2^(2^n)+a(n) is a probable prime. By a comment in A000215, a(n) is not 2^m+1 for any m > 1. - T. D. Noe, Jul 19 2007
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LINKS
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MATHEMATICA
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a[n_] := Module[{k = 0}, While[! PrimeQ[2^(2^n) + k], k++]; k]; Array[a, 12, 0] (* Amiram Eldar, Jun 11 2022 *)
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PROG
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(PARI) a(n)=if(n<0, 0, s=0; while(isprime(2^(2^n)+s)==0, s++); s)
(Python)
from sympy import nextprime
def a(n): m = 2**(2**n); return nextprime(m-1) - m
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CROSSREFS
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Cf. A013597 (least k>0 such that 2^n+k is prime).
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KEYWORD
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nonn,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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