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A034816 Concatenations C1 and C2 are both prime (see the comment lines). 0
9, 51, 63, 117, 123, 157, 183, 213, 217, 219, 257, 263, 321, 327, 333, 423, 441, 473, 541, 597, 621, 687, 693, 723, 777, 879, 909, 987, 1101, 1143, 1187, 1387, 1459, 1551, 1887, 2127, 2179, 2193, 2817, 3197, 3339, 3513, 3633, 4029, 4209, 4429, 4529, 4557 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

C1 = 'prevprime(n) followed by n'

C2 = 'n followed by nextprime(n)'

LINKS

Table of n, a(n) for n=0..47.

EXAMPLE

n=1551 -> previous prime is 1549, next prime is 1553, thus '15491551' and '15511553' are both primes.

CROSSREFS

Cf. A034808-A034821.

Sequence in context: A002462 A210061 A034814 * A140381 A330805 A282877

Adjacent sequences: A034813 A034814 A034815 * A034817 A034818 A034819

KEYWORD

nonn,base

AUTHOR

Patrick De Geest, Oct 15 1998

STATUS

approved

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Last modified March 24 08:50 EDT 2023. Contains 361463 sequences. (Running on oeis4.)