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A034813 Concatenations C1 and C2 are both prime (see the comment lines). 1
36, 74, 104, 132, 188, 222, 224, 305, 317, 344, 367, 368, 389, 457, 458, 475, 540, 572, 584, 608, 631, 676, 682, 689, 697, 738, 756, 760, 781, 797, 829, 841, 893, 910, 911, 914, 928, 982, 1018, 1104, 1122, 1178, 1186, 1317, 1328, 1391, 1402, 1406, 1518 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

C1 = 'prevprime(n) followed by n followed by nextprime(n)'

C2 = 'nextprime(n) followed by n followed by prevprime(n)'

LINKS

Harvey P. Dale, Table of n, a(n) for n = 0..1000

EXAMPLE

n=797 -> previous prime is 787, next prime is 809, thus '787797809' and '809797787' are both primes.

MATHEMATICA

c1c2Q[n_]:=Module[{ia=IntegerDigits[NextPrime[n, -1]], ib=IntegerDigits[n], ic= IntegerDigits[NextPrime[n]]}, AllTrue[{FromDigits[Join[ia, ib, ic]], FromDigits[Join[ic, ib, ia]]}, PrimeQ]]; Select[Range[1600], c1c2Q] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Apr 06 2018 *)

CROSSREFS

Cf. A034808-A034821.

Sequence in context: A024975 A025399 A171390 * A319602 A262796 A255101

Adjacent sequences:  A034810 A034811 A034812 * A034814 A034815 A034816

KEYWORD

nonn,base

AUTHOR

Patrick De Geest, Oct 15 1998

STATUS

approved

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Last modified November 17 08:39 EST 2019. Contains 329217 sequences. (Running on oeis4.)