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A032664 Digit '1' concatenated with a(n) is a prime. 4
1, 3, 7, 9, 13, 27, 31, 37, 39, 49, 51, 57, 63, 67, 73, 79, 81, 91, 93, 97, 99, 103, 109, 117, 123, 129, 151, 153, 163, 171, 181, 187, 193, 201, 213, 217, 223, 229, 231, 237, 249, 259, 277, 279, 283, 289, 291, 297, 301, 303, 307, 319, 321, 327, 361, 367, 373 (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[400], PrimeQ[10^IntegerLength[#]+#]&] (* Harvey P. Dale, Dec 16 2019 *)

CROSSREFS

Sequence in context: A110575 A325556 A174840 * A166733 A172987 A118556

Adjacent sequences:  A032661 A032662 A032663 * A032665 A032666 A032667

KEYWORD

nonn,base

AUTHOR

Patrick De Geest, May 15 1998

EXTENSIONS

Edited by Charles R Greathouse IV, Apr 24 2010

STATUS

approved

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Last modified September 28 01:04 EDT 2020. Contains 337388 sequences. (Running on oeis4.)