A102764 Numbers k such that k7777777 is prime.

13, 19, 30, 34, 43, 52, 54, 57, 58, 64, 69, 78, 82, 94, 96, 124, 145, 148, 157, 165, 177, 178, 187, 192, 195, 201, 202, 243, 246, 250, 256, 264, 277, 291, 303, 307, 313, 319, 324, 325, 340, 342, 352, 355, 382, 393, 397, 402, 409, 429, 430, 432, 444, 456, 468, 474, 486, 493, 499, 517

Offset: 1

Author

Parthasarathy Nambi, Feb 25 2005

Keywords

• base
• nonn

Examples

			If k=13, then k7777777 = 137777777 (prime).
If k=57, then k7777777 = 577777777 (prime).
If k=96, then k7777777 = 967777777 (prime).
		

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000

Programs

Magma

[ n: n in [1..700] | IsPrime(Seqint([7,7,7,7,7,7,7] cat Intseq(n))) ]; // Vincenzo Librandi, Feb 03 2011

Mathematica

Select[Range[600],PrimeQ[#*10^7+7777777]&] (* Harvey P. Dale, Jan 02 2015 *)