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A069833
Prefixing, suffixing or inserting a 9 in the number anywhere gives a prime.
9
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
OFFSET
1,1
LINKS
Giovanni Resta, Table of n, a(n) for n = 1..2128 (terms < 10^13, first 1175 terms from Chai Wah Wu)
PROG
(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
CROSSREFS
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
KEYWORD
nonn,base
AUTHOR
Amarnath Murthy, Apr 14 2002
EXTENSIONS
More terms from Vladeta Jovovic, Apr 16 2002
Corrected offset by Chai Wah Wu, Oct 10 2019
STATUS
approved