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 A100014 Least a(n) such that a(n)*2^n*(2^n-1)+1 is prime. 1
 1, 1, 2, 1, 6, 3, 5, 12, 3, 5, 8, 6, 5, 3, 18, 8, 41, 5, 11, 14, 66, 8, 2, 9, 18, 8, 21, 12, 30, 16, 6, 1, 6, 8, 33, 2, 53, 23, 2, 5, 21, 15, 6, 12, 20, 5, 5, 28, 53, 80, 11, 53, 9, 5, 56, 2, 120, 5, 23, 16, 9, 8, 5, 9, 24, 25, 62, 131, 41, 51, 12, 3, 99, 56, 2, 37, 155, 3, 23, 55, 29, 9, 2, 33 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Numbers n such that a(n)=2 are found in A006598. - Michel Marcus, Mar 07 2013 LINKS EXAMPLE 1*2^5*(2^5-1)+1=993=3*331 2*2^5*(2^5-1)+1=1985=5*397 3*2^5*(2^5-1)+1=2977=13*229 4*2^5*(2^5-1)+1=3969=3*1323 5*2^5*(2^5-1)+1=4961=11*451 6*2^5*(2^5-1)+1=5953 prime so a(5)=6 PROG (PARI) a(n) = {k = 1; while (! isprime(k*2^n*(2^n-1) + 1), k++); return (k); } \\ Michel Marcus, Mar 07 2013 CROSSREFS Sequence in context: A097288 A223894 A171178 * A062566 A126265 A124441 Adjacent sequences:  A100011 A100012 A100013 * A100015 A100016 A100017 KEYWORD easy,nonn AUTHOR Pierre CAMI, Nov 18 2004 STATUS approved

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