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

1,1

Links

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

Example

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

Mathematica

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

Prog

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

Crossrefs

Sequence in context: A141562 A353205 A108097 * A164318 A307533 A092738

Adjacent sequences: A102761 A102762 A102763 * A102765 A102766 A102767

Keyword

base,nonn

Author

Parthasarathy Nambi, Feb 25 2005

Status

approved