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A111051
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Numbers n such that 3*n^2 + 1 is prime.
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5
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2, 6, 8, 12, 16, 20, 22, 26, 34, 36, 40, 58, 64, 68, 78, 82, 84, 86, 98, 112, 120, 126, 142, 146, 148, 152, 156, 160, 168, 188, 190, 194, 196, 208, 216, 218, 222, 238, 240, 244, 246, 254, 264, 272, 282, 286, 294, 300, 302, 306, 308, 316, 320, 330, 338, 344, 348
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OFFSET
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1,1
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COMMENTS
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The resulting primes are the generalized cuban primes of the form p = (x^3 - y^3 )/(x - y), x=y+2 (see A002648). - Jani Melik, Jul 18 2007
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LINKS
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Zak Seidov, Table of n, a (n) for n = 1..1000
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EXAMPLE
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a(1)=2 because p = 1+3*2^2 = 13 is prime.
a(2)=6 because p = 1+3*6^2 = 109 is prime.
a(3)=8 because p = 1+3*8^2 = 193 is prime.
If n=98 then (3*n^2) + 1 = 28813 (prime).
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MAPLE
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ts_kubpra_ind:=proc(n) local i, tren, ans; ans:=[ ]: for i from 0 to n do tren:=1+3*i^2: if (isprime(tren)='true') then ans:=[ op(ans), i ] fi od: RETURN(ans); end: ts_kubpra_ind(2000); - Jani Melik, Jul 18 2007
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CROSSREFS
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Cf. A002648.
Sequence in context: A057656 A084724 A189400 * A077561 A008407 A111224
Adjacent sequences: A111048 A111049 A111050 * A111052 A111053 A111054
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KEYWORD
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nonn
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AUTHOR
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Parthasarathy Nambi, Oct 06 2005
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EXTENSIONS
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More terms from Jani Melik, Jul 18 2007
Edited by N. J. A. Sloane, Sep 28 2007
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STATUS
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approved
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