A154408 Primes p such that (p^2 + 1)/10 is also prime.

7, 13, 17, 23, 37, 53, 67, 97, 103, 113, 127, 137, 163, 167, 197, 223, 227, 263, 277, 283, 347, 367, 373, 383, 397, 433, 503, 547, 587, 617, 653, 673, 677, 683, 773, 797, 823, 877, 883, 937, 947, 953, 997, 1063, 1103, 1117, 1163, 1187, 1213, 1367, 1423, 1447

Offset

1,1

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Example

37 is in the sequence because both 37 and (37^2 + 1)/10 = 137 are primes. [Emeric Deutsch, Jan 21 2009]

Maple

a := proc (n) if isprime(n) = true and type((1/10)*n^2+1/10, integer) = true and isprime((1/10)*n^2+1/10) = true then n else end if end proc: seq(a(n), n = 2 .. 1700); # Emeric Deutsch, Jan 21 2009

Mathematica

Select[Prime[Range[200]], PrimeQ[(#^2 + 1)/10] &] (* Vincenzo Librandi, Oct 15 2012 *)

Prog

(Magma) [p: p in PrimesInInterval(7, 2500) | IsPrime((p^2 + 1) div 10)]; // Vincenzo Librandi, Oct 15 2012

Crossrefs

Cf. A017305.

Sequence in context: A136083 A167276 A181570 * A089531 A247010 A138337

Adjacent sequences: A154405 A154406 A154407 * A154409 A154410 A154411

Keyword

nonn,easy

Author

Vincenzo Librandi, Jan 09 2009

Extensions

Corrected and extended by Emeric Deutsch, Jan 21 2009

Status

approved