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A117048
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Prime numbers which are expressible as the sum of two positive triangular numbers.
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6
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2, 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
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| If the triangular number 0 is allowed, only one additional prime occurs: 3. In that case, the sequence becomes A117112.
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LINKS
| T. D. Noe, Table of n, a(n) for n = 1..10000
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EXAMPLE
| 2 = 1 + 1
7 = 1 + 6
11 = 1 + 10
13 = 10 + 3, etc.
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MATHEMATICA
| tri = Table[n (n + 1)/2, {n, 40}]; Select[Union[Flatten[Outer[Plus, tri, tri]]], # <= tri[[-1]]+1 && PrimeQ[#] &] (* T. D. Noe, Apr 07 2011 *)
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CROSSREFS
| Cf. A000040, A000217, A002243, A002244, A020756, A053614, A060773, A002636.
Sequence in context: A045369 A157975 A045370 * A040128 A140548 A018308
Adjacent sequences: A117045 A117046 A117047 * A117049 A117050 A117051
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KEYWORD
| easy,nonn
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AUTHOR
| Andrew Plewe (aplewe(AT)sbcglobal.net), Apr 15 2006
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