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A069833
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Prefixing, suffixing or inserting a 9 in the number anywhere gives a prime.
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9
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7, 19, 37, 41, 91, 199, 209, 239, 311, 539, 587, 661, 749, 923, 931, 941, 967, 1009, 1079, 1139, 1997, 2717, 2959, 3971, 3979, 4559, 4993, 4999, 5393, 5629, 5651, 6401, 6739, 6911, 8213, 8491, 8939, 9109, 9397, 9607, 9679, 9829, 11089, 11227, 13943
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OFFSET
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1,1
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LINKS
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Giovanni Resta, Table of n, a(n) for n = 1..2128 (terms < 10^13, first 1175 terms from Chai Wah Wu)
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PROG
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(PARI) is(n, L=logint(n+!n, 10)+1, d, P)={!for(k=0, L, isprime((d=divrem(n, P=10^(L-k)))[2]+(10*d[1]+9)*P)||return)} \\ M. F. Hasler, May 10 2018
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CROSSREFS
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Cf. A215421 (subsequence of primes).
Cf. A068679 (1 is prefixed, appended or inserted anywhere), A069246 (primes among these), A068673 (1 is prefixed, or appended).
Cf. A158594 (3 is prefixed, appended or inserted anywhere), A215419 (primes among these).
Cf. A069832 (7 is prefixed, appended or inserted anywhere), A215420 (primes among these), A068677 (7 is prefixed or appended).
Cf. A158232 (13 is prefixed or appended).
Cf. A164329 (0 is inserted), A216169 (subset of composite terms), A215417 (subset of primes), A159236 (0 is inserted between all digits).
Sequence in context: A124270 A298565 A068678 * A215421 A192594 A352243
Adjacent sequences: A069830 A069831 A069832 * A069834 A069835 A069836
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KEYWORD
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nonn,base
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AUTHOR
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Amarnath Murthy, Apr 14 2002
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EXTENSIONS
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More terms from Vladeta Jovovic, Apr 16 2002
Corrected offset by Chai Wah Wu, Oct 10 2019
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STATUS
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approved
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