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A104635
Odd n such that 2*n+1 is prime.
7
1, 3, 5, 9, 11, 15, 21, 23, 29, 33, 35, 39, 41, 51, 53, 63, 65, 69, 75, 81, 83, 89, 95, 99, 105, 111, 113, 119, 125, 131, 135, 141, 153, 155, 165, 173, 179, 183, 189, 191, 209, 215, 219, 221, 231, 233, 239, 243, 245, 249, 251, 261, 273, 281, 285, 293, 299
OFFSET
1,2
COMMENTS
Also: Numbers k such that 2k+1 is in A002145, i.e., a Gaussian prime. - M. F. Hasler, Feb 25 2011
Also: Number of quadratic residues modulo A002145(n). - M. F. Hasler, Feb 25 2011
LINKS
FORMULA
a(n) = floor(A002145(n)/2). - M. F. Hasler, Feb 25 2011
MATHEMATICA
Select[Range[1, 301, 2], PrimeQ[2#+1]&] (* Harvey P. Dale, May 08 2012 *)
PROG
(PARI) forstep( k=1, 250, 2, isprime(2*k+1) && print1(k", ")) \\ M. F. Hasler, Feb 25 2011
(PARI) forprime( p=1, 500, p%4==3 || next; print1(p\2", ")) \\ M. F. Hasler, Feb 25 2011
(Magma) [n: n in [1..500 by 2] | IsPrime(2*n+1)]; // Vincenzo Librandi, Aug 14 2018
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Zak Seidov, Mar 18 2005
STATUS
approved