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 A020454 Primes that contain digits 1 and 6 only. 5
 11, 61, 661, 6661, 11161, 16111, 16661, 66161, 111611, 161611, 611111, 616111, 1111661, 1611161, 1616161, 1616611, 1661111, 1661161, 1666111, 6111661, 6116111, 6116161, 6161161, 6611611, 6661111, 6661661, 11111161, 11166611, 11616611 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..1000 MATHEMATICA Flatten[Table[Select[FromDigits/@Tuples[{1, 6}, n], PrimeQ], {n, 8}]] (* Vincenzo Librandi, Jul 27 2012 *) Select[Flatten[Table[10*FromDigits/@Tuples[{1, 6}, n]+1, {n, 7}]], PrimeQ] (* Slightly faster than the above Mathematica program by forcing the last digit to be one. *) (* Harvey P. Dale, May 31 2018 *) PROG (MAGMA) [p: p in PrimesUpTo(11616611) | Set(Intseq(p)) subset [1, 6]]; // Vincenzo Librandi, Jul 27 2012. (see Berselli A020461). CROSSREFS Sequence in context: A088545 A259257 A289646 * A009016 A191596 A227087 Adjacent sequences:  A020451 A020452 A020453 * A020455 A020456 A020457 KEYWORD nonn,base AUTHOR STATUS approved

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Last modified July 20 14:09 EDT 2019. Contains 325181 sequences. (Running on oeis4.)