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A084413 Smallest prime with "n" as central digit(s). 3
101, 113, 2, 3, 149, 5, 163, 7, 181, 191, 1103, 11, 1123, 13, 2141, 1151, 1163, 17, 1181, 19, 1201, 1213, 1223, 23, 1249, 1259, 2267, 1277, 1283, 29, 1301, 31, 1321, 2333, 2341, 2351, 1361, 37, 1381, 1399, 1409, 41, 1423, 43, 1447, 1451, 2467, 47, 1481 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

LINKS

Table of n, a(n) for n=0..48.

FORMULA

If n is prime, then a(n) = n, else a(n) = A084414(n). - Michel Marcus, Oct 05 2013

EXAMPLE

a(1)=113 because 113 is the smallest prime with "1" as central digit.

a(10)=1103 because 1103 is the smallest prime with "10" as central digits.

PROG

(PARI) findex(n) = {for (i = 1, 9, forstep (j=1, 9, 2, v = j + 10*n + i*10^(1+length(Str(n))); if (isprime(v), return (v)); ); ); }

a(n) = if (isprime(n), n, findex(n)); \\ code assumes only 1 digit on each side of 'n' will be necessary. See A032734 for numbers that need a better script. - Michel Marcus, Oct 05 2013

CROSSREFS

Sequence in context: A267585 A294743 A214527 * A248533 A069691 A084414

Adjacent sequences:  A084410 A084411 A084412 * A084414 A084415 A084416

KEYWORD

easy,nonn,base

AUTHOR

Zak Seidov, Jun 24 2003

STATUS

approved

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Last modified July 21 02:02 EDT 2019. Contains 325189 sequences. (Running on oeis4.)