OFFSET
1,1
LINKS
Giovanni Resta, Table of n, a(n) for n = 1..10000
MATHEMATICA
Select[Range[2*10^6], PrimeQ[Sqrt[#-1]]&&PrimeQ[#/2]&] (* Ivan N. Ianakiev, Jul 13 2015 *)
Select[Prime@ Range[10^4], PrimeQ[(#^2 + 1)/2] &]^2 + 1 (* faster, Giovanni Resta, Jul 13 2015 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Jul 12 2015, following a suggestion of R. P. Boas, May 19, 1974
EXTENSIONS
Corrected and extended by Ivan N. Ianakiev, Jul 13 2015
STATUS
approved