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A089008 Numbers n such that 18*n^2 + 1 is prime. 4
1, 2, 3, 7, 8, 9, 10, 11, 12, 14, 15, 22, 24, 25, 29, 31, 32, 33, 34, 35, 41, 44, 45, 51, 52, 54, 59, 62, 63, 67, 68, 73, 76, 79, 80, 85, 88, 91, 95, 99, 100, 102, 107, 108, 109, 117, 119, 120, 122, 125, 129, 131, 133, 135, 139, 141, 142, 143, 147, 150, 152, 154, 156 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

There are 8 consecutive terms at n=13537 and n=105819293 for n<10^9. - Jean C. Lambry, Oct 19 2015

LINKS

Zak Seidov, Table of n, a(n) for n = 1..1000.

FORMULA

a(n) = A089001(n+1)/3.

MATHEMATICA

Select[Range[200], PrimeQ[18#^2+1]&]  (* Harvey P. Dale, Apr 25 2011 *)

PROG

(PARI) for(n=0, 1e3, if(isprime(k=(18*n^2 + 1)), print1(n", "))) \\ Altug Alkan, Oct 19 2015

CROSSREFS

Cf. A089001, A090612, A090698.

Sequence in context: A324777 A244162 A182516 * A228088 A299497 A047534

Adjacent sequences:  A089005 A089006 A089007 * A089009 A089010 A089011

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Dec 20 2003

STATUS

approved

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Last modified February 17 12:32 EST 2020. Contains 331996 sequences. (Running on oeis4.)