A032670 - OEIS

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A032670

Digit '7' concatenated with a(n) is a prime.

1, 3, 9, 19, 27, 33, 39, 43, 51, 57, 61, 69, 73, 87, 97, 103, 109, 121, 127, 129, 151, 159, 177, 187, 193, 207, 211, 213, 219, 229, 237, 243, 247, 253, 283, 297, 307, 309, 321, 331, 333, 349, 351, 369, 393, 411, 417, 433, 451, 457, 459, 477, 481

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

LINKS

Seiichi Manyama, Table of n, a(n) for n = 1..10000

MATHEMATICA

Select[Range[500], PrimeQ[7*10^IntegerLength[#]+#]&] (* Harvey P. Dale, Sep 16 2020 *)

CROSSREFS

Sequence in context: A056259 A376220 A056682 * A068677 A069832 A057257

Adjacent sequences: A032667 A032668 A032669 * A032671 A032672 A032673

KEYWORD

nonn,base

AUTHOR

Patrick De Geest, May 15 1998

STATUS

approved