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A088502
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Numbers n such that (n^2 - 5)/4 is prime.
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3
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5, 7, 9, 11, 13, 17, 19, 21, 23, 27, 31, 33, 39, 41, 43, 49, 53, 57, 61, 63, 71, 77, 79, 83, 89, 91, 93, 97, 101, 107, 109, 111, 113, 119, 121, 129, 131, 133, 137, 141, 153, 167, 171, 173, 179, 187, 189, 193, 201, 203, 207, 229, 231, 241, 251, 253, 261, 263, 269
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Under Bunyakovsky's conjecture this sequence is infinite. [Charles R Greathouse IV, Dec 28 2011]
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FORMULA
| a(n) = 2*A002328(n) - 1 = Sqrt(A110013(n)). - Ray Chandler (rayjchandler(AT)sbcglobal.net), Sep 07 2005
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EXAMPLE
| (23*23 - 5)/4 = 131, 131 is prime, 23 is the 9-th n of the sequence.
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PROG
| (PARI) for(k=2, 1e3, if(isprime(k^2+k-1), print1(2*k+1", "))) \\ Charles R Greathouse IV, Dec 28 2011
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CROSSREFS
| Cf. A002327, A002328, A110013.
Sequence in context: A005763 A035034 A065155 * A081001 A075025 A075394
Adjacent sequences: A088499 A088500 A088501 * A088503 A088504 A088505
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KEYWORD
| easy,nonn
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AUTHOR
| Pierre CAMI (colettecami(AT)aol.com), Nov 13 2003
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