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 A102764 Numbers k such that k7777777 is prime. 2
 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 (list; graph; refs; listen; history; text; internal format)
 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

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Last modified May 22 06:54 EDT 2022. Contains 353933 sequences. (Running on oeis4.)