login
A259979
Numbers that are both 1 + square of a prime and twice a prime.
1
10, 26, 122, 362, 842, 3482, 3722, 5042, 6242, 10202, 17162, 19322, 32762, 39602, 73442, 121802, 143642, 167282, 201602, 212522, 271442, 323762, 326042, 398162, 410882, 436922, 546122, 564002, 674042, 776162, 863042, 982082, 1062962, 1079522, 1104602, 1142762, 1190282, 1274642, 1324802, 1371242
OFFSET
1,1
LINKS
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
Sequence in context: A051966 A221568 A092774 * A368503 A235053 A217583
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