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A117112
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Primes expressible as the sum of two triangular numbers (including zero).
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6
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2, 3, 7, 11, 13, 29, 31, 37, 43, 61, 67, 73, 79, 83, 97, 101, 127, 137, 139, 151, 157, 163, 181, 191, 193, 199, 211, 227, 241, 263, 277, 281, 307, 331, 353, 367, 373, 379, 389, 409, 421, 433, 443, 461, 463, 487, 499, 541, 571, 577, 587, 601, 619, 631, 659, 661
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OFFSET
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1,1
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COMMENTS
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See A117048 for the primes that are the sum of two positive triangular numbers. The only difference is that the prime 3 occurs here.
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LINKS
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Table of n, a(n) for n=1..56.
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FORMULA
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A000040 intersect A020756. - Jonathan Vos Post, Apr 17 2006
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EXAMPLE
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2 = 1 + 1
3 = 0 + 3
7 = 1 + 6
and so on.
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MATHEMATICA
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tri = Table[n (n + 1)/2, {n, 0, 40}]; Select[Union[Flatten[Outer[Plus, tri, tri]]], # <= tri[[-1]]+1 && PrimeQ[#] &] (* T. D. Noe, Apr 07 2011 *)
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CROSSREFS
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Cf. A000217, A117048.
Sequence in context: A091206 A038963 A167609 * A145032 A038895 A113244
Adjacent sequences: A117109 A117110 A117111 * A117113 A117114 A117115
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KEYWORD
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easy,nonn
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AUTHOR
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Greg Huber (huber(AT)alum.mit.edu), Apr 18 2006
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STATUS
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approved
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