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A275680 Nonprime integers that become prime when concatenated with the next digit. 1
1, 9, 70, 10, 12, 72, 74, 30, 75, 14, 90, 76, 15, 16, 33, 18, 100, 91, 92, 93, 77, 34, 78, 700, 102, 104, 94, 105, 106, 35, 36, 702, 703, 95, 38, 39, 704, 300, 108, 705, 706, 96, 707, 98, 301, 99, 110, 302, 303, 710, 304, 111, 712, 112, 306, 115, 116, 308, 310, 900, 117, 118, 119, 312, 120, 121, 316, 318, 122, 319, 123, 124, 901, 125, 902, 904 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

The sequence is started with a(1) = 1 and always extended with the smallest integer not yet present that does not lead to a contradiction.

LINKS

Jean-Marc Falcoz, Table of n, a(n) for n = 1..10001

EXAMPLE

1 is not prime but 19 is [1,9].

9 is not prime but 97 is [9,7(0)].

70 is not prime but 701 is [70,1(0)].

10 is not prime but 101 is [10,1(2)].

12 is not prime but 127 is [12,7(2)].

72 is not prime but 727 is [72,7(4)].

74 is not prime but 743 is [74,3(0)].

30 is not prime but 307 is [30,7(5)].

75 is not prime but 751 is [75,1(4)].

14 is not prime but 149 is [14,9(0)].

...

CROSSREFS

Sequence in context: A152273 A217452 A193706 * A167534 A110202 A110201

Adjacent sequences:  A275677 A275678 A275679 * A275681 A275682 A275683

KEYWORD

nonn,base

AUTHOR

Eric Angelini and Jean-Marc Falcoz, Aug 05 2016

STATUS

approved

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Last modified February 25 22:44 EST 2020. Contains 332270 sequences. (Running on oeis4.)