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A237759 Numbers n such that either n^2*2^n-1 or n^2*2^n+1 is prime, but not both. 0
1, 2, 4, 7, 21, 25, 30, 33, 41, 45, 57, 63, 83, 100, 131, 142, 144, 147, 150, 175, 198, 225, 304, 425, 449, 469, 513, 651, 782, 858, 1345, 1839, 1883, 1913, 2177, 2551, 2907, 3638, 3675, 6071, 6076, 9297, 11037, 11743, 12135, 12876, 14641, 38685, 40857 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..49.

EXAMPLE

4 is in the sequence because 4^2*2^4 - 1 = 16*16 - 1 = 255 is not a prime number but 4^2*2^4 + 1 = 16*16 + 1 = 257 is a prime number.

PROG

(PARI) isok(n) = isp1 = isprime(2^n*n^2-1); isp2 = isprime(2^n*n^2+1); (isp1 || isp2 && !(isp1 && isp2)); \\ Michel Marcus, Mar 05 2014

CROSSREFS

Cf, A058781, A058780.

Sequence in context: A101805 A145777 A188497 * A306978 A153550 A102984

Adjacent sequences:  A237756 A237757 A237758 * A237760 A237761 A237762

KEYWORD

nonn,less

AUTHOR

Juri-Stepan Gerasimov, Feb 24 2014

EXTENSIONS

Corrected by R. J. Mathar, Feb 26 2014

STATUS

approved

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Last modified April 8 04:26 EDT 2020. Contains 333312 sequences. (Running on oeis4.)