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A117112 Primes expressible as the sum of two triangular numbers (including zero). 6
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

See A117048 for the primes that are the sum of two positive triangular numbers. The only difference is that the prime 3 occurs here.

LINKS

Table of n, a(n) for n=1..56.

FORMULA

A000040 intersect A020756. - Jonathan Vos Post, Apr 17 2006

EXAMPLE

2 = 1 + 1

3 = 0 + 3

7 = 1 + 6

and so on.

MATHEMATICA

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 *)

CROSSREFS

Cf. A000217, A117048.

Sequence in context: A091206 A038963 A167609 * A145032 A233414 A233863

Adjacent sequences:  A117109 A117110 A117111 * A117113 A117114 A117115

KEYWORD

easy,nonn

AUTHOR

Greg Huber, Apr 18 2006

STATUS

approved

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Last modified October 24 20:44 EDT 2014. Contains 248516 sequences.