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

Author

Vincenzo Librandi, Jan 09 2009

Keywords

• nonn
• easy

Examples

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

Links

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

Crossrefs

Cf. A017305.

Programs

Magma

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

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 *)

Extensions

Corrected and extended by Emeric Deutsch, Jan 21 2009