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A226070
Numbers n such that n^2-1 is a triangular number and n^2+1 is a prime.
3
1, 2, 4, 134, 2174, 154634
OFFSET
1,2
COMMENTS
Subsequence of A006452 that consists of the terms n such that n^2+1 is prime.
a(7) is too large to include here (see b-file). - Max Alekseyev, Jan 30 2014
LINKS
MATHEMATICA
Select[Range[155000], PrimeQ[#^2+1]&&OddQ[Sqrt[8(#^2-1)+1]]&] (* Harvey P. Dale, Jul 19 2019 *)
PROG
(C) // see A226069.
CROSSREFS
Corresponding primes: A226069.
Indices of corresponding triangular numbers: A226071.
Sequence in context: A018500 A353790 A271677 * A013552 A018512 A018517
KEYWORD
nonn
AUTHOR
Alex Ratushnyak, May 25 2013
EXTENSIONS
Terms a(7)-a(12) from Max Alekseyev, Jan 30 2014
STATUS
approved