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A125602
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Prime centered triangular numbers.
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4
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19, 31, 109, 199, 409, 571, 631, 829, 1489, 1999, 2341, 2971, 3529, 4621, 4789, 7039, 7669, 8779, 9721, 10459, 10711, 13681, 14851, 16069, 16381, 17659, 20011, 20359, 23251, 25939, 27541, 29191, 29611, 31321, 34429, 36739, 40099, 40591, 42589
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OFFSET
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1,1
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COMMENTS
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Or prime terms in A005448, or primes of the form 3n(n-1)/2 + 1.
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LINKS
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Vincenzo Librandi, Table of n, a(n) for n = 1..1000
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MATHEMATICA
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lst={}; Do[If[PrimeQ[p=3n(n-1)/2+1], (*Print[p]; *)AppendTo[lst, p]], {n, 10^3}]; lst [From Vladimir Joseph Stephan Orlovsky, Aug 21 2008]
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PROG
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(MAGMA) [a: n in [0..200] | IsPrime(a) where a is (3*n^2 - 3*n + 2) div 2]; // Vincenzo Librandi, Mar 22 2013
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CROSSREFS
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Cf. A005448, A125603.
Sequence in context: A032743 A106861 A107168 * A139847 A087764 A146691
Adjacent sequences: A125599 A125600 A125601 * A125603 A125604 A125605
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KEYWORD
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nonn,easy
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AUTHOR
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Zak Seidov, Nov 27 2006
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STATUS
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approved
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