OFFSET
1,1
LINKS
J. Mulder, Table of n, a(n) for n = 1..50000
FORMULA
EXAMPLE
3 is in the sequence because 3+(3^2-1)/4=5 is a prime number.
5 is in the sequence because 5+(5^2-1)/4=11 is a prime number.
MATHEMATICA
f[n_]:=((p+1)/2)^2+((p-1)/2); lst={}; Do[p=Prime[n]; If[PrimeQ[f[p]], AppendTo[lst, p]], {n, 6!}]; lst
Select[Range[700], PrimeQ[#] && PrimeQ[# + (#^2 - 1)/4] &] (* Vincenzo Librandi, Apr 08 2013 *)
Select[Prime[Range[200]], PrimeQ[#+(#^2-1)/4]&] (* Harvey P. Dale, Jun 18 2014 *)
PROG
(Magma) [p: p in PrimesInInterval(3, 1000) | IsPrime(p+(p^2-1) div 4)]; // Vincenzo Librandi, Apr 08 2013
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Vladimir Joseph Stephan Orlovsky, Jul 27 2009
EXTENSIONS
Definition simplified by R. J. Mathar, Aug 17 2009
STATUS
approved