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A259534
a(n) = -1 + 2 * product_{i=0..n} A093179(i), where A093179(i) is the smallest prime factor of 2^(2^i) + 1.
0
5, 29, 509, 131069, 8589934589, 5506148072189, 1509659159988837629, 90050548615896750734368618889875709, 111565998552535226317138856424609779410946920431869, 270528914968139650436266764640655805238384653911572627709
OFFSET
0,1
COMMENTS
For any k >= 1, numbers of the form (k*a(n) + k - 1)*2^m - 1 are composite for all m < 2^(n+1).
Many terms are in common with A006285 (de Polignac numbers).
PROG
(PARI) a(n) = - 1 + 2 * prod(k=0, n, factor(2^(2^k)+1)[1, 1]); \\ Michel Marcus, Jul 04 2015
CROSSREFS
Sequence in context: A198054 A202758 A197962 * A176680 A352948 A352951
KEYWORD
nonn
AUTHOR
STATUS
approved