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A356293
Primes p such that if q is the next prime, (p+q)/6 is a triangular number.
1
7, 17, 29, 43, 107, 163, 197, 313, 457, 569, 757, 827, 1303, 1487, 1783, 1997, 2339, 2707, 2969, 3527, 3673, 3967, 4289, 4787, 5119, 5857, 7243, 9007, 9719, 10457, 10709, 10957, 12281, 13679, 16067, 17657, 20357, 21773, 23623, 27127, 27539, 31319, 33073, 33521, 37201, 38153, 45673, 48869, 50503
OFFSET
1,1
COMMENTS
Primes p such that, if q is the next prime, 1+4*(p+q)/3 is a square.
LINKS
EXAMPLE
a(3) = 29 is a term because 29 is prime, the next prime is 31, and (29+31)/6 = 10 is a triangular number.
MAPLE
P:= select(isprime, [seq(i, i=3..10^5, 2)]):
S:= (P[1..-2]+P[2..-1])/3:
P[select(i -> S[i]::integer and issqr(1+4*S[i]), [$1..nops(S)])];
MATHEMATICA
Select[Partition[Prime[Range[5000]], 2, 1], IntegerQ[Sqrt[4*Total[#]/3 + 1]] &][[;; , 1]] (* Amiram Eldar, Aug 03 2022 *)
CROSSREFS
Cf. A000217.
Sequence in context: A217926 A250294 A157417 * A294133 A088566 A059845
KEYWORD
nonn
AUTHOR
J. M. Bergot and Robert Israel, Aug 02 2022
STATUS
approved