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A090562
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Primes of the form 5k^2 + 5k + 1
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12
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11, 31, 61, 101, 151, 211, 281, 661, 911, 1051, 1201, 1361, 1531, 1901, 2311, 2531, 3001, 3251, 3511, 4651, 5281, 6301, 6661, 7411, 9461, 9901, 12251, 13781, 14851, 15401, 18301, 18911, 19531, 20161, 22111, 24151, 24851, 25561, 27011, 27751
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Or, primes obtained as a concatenation of a triangular number and 1.
Centered decagonal primes. - Paul Muljadi (paulmuljadi(AT)yahoo.com), Oct 04 2005
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LINKS
| Vincenzo Librandi, Table of n, a(n) for n = 1..5000
Wikipedia, Centered decagonal number.
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MATHEMATICA
| Select[5(#^2 - #) + 1 & /@ Range[75], PrimeQ[ # ] &] (* Robert G. Wilson v *)
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PROG
| (MAGMA) [a: n in [0..100] | IsPrime(a) where a is 5*n^2 + 5*n + 1]; // Vincenzo Librandi, Dec 13 2011
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CROSSREFS
| Cf. A090563.
Sequence in context: A202007 A125239 A062786 * A174244 A136061 A090233
Adjacent sequences: A090559 A090560 A090561 * A090563 A090564 A090565
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KEYWORD
| easy,nonn
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AUTHOR
| Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Dec 11 2003
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EXTENSIONS
| Edited and extended by Robert G. Wilson v (rgwv(at)rgwv.com), Oct 10 2005)
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