OFFSET
1,1
LINKS
Robert Israel, Table of n, a(n) for n = 1..1525
EXAMPLE
From Jon E. Schoenfield, Jan 24 2018: (Start)
prime(8) = 19 = 2*3^2 + 1, so 8 is in the sequence.
prime(21) = 73 = 2*6^2 + 1, so 21 is in the sequence.
prime(33) = 137 = 2*68 + 1, and 68 is not a square, so 33 is not in the sequence. (End)
MAPLE
N:= 1000; # to get all entries corresponding to primes <= 2*N^2+1.
R:= select(isprime, [seq(2*k^2+1, k=1..N)]):
A090612:= map(numtheory[pi], R); # Robert Israel, May 09 2014
MATHEMATICA
Select[Range[18000], IntegerQ[Sqrt[(Prime[#]-1)/2]]&] (* Harvey P. Dale, Apr 25 2016 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Ray Chandler, Dec 21 2003
STATUS
approved