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A034818 Concatenations C1 and C2 and C3 are all prime (see the comment lines). 0
657, 4929, 10647, 18291, 20907, 22653, 27381, 28053, 28671, 42471, 48441, 57363, 69651, 79569, 89853, 93261, 95967, 101283, 110763, 119481, 128613, 145719, 149409, 174993, 201417, 204861, 205329, 221883, 248391, 269199, 272799, 293451 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

C1 = 'nextprime(n) followed by n'

C2 = 'n followed by prevprime(n)'

C3 = 'nextprime(n) followed by n followed by prevprime(n)'

LINKS

Table of n, a(n) for n=0..31.

EXAMPLE

n=95967 -> next prime is 95971, previous prime is 95959, thus '9597195967' and '9596795959' and '959719596795959' are all three primes.

MATHEMATICA

ccatQ[n_]:=Module[{idn=IntegerDigits[n], pp=IntegerDigits[NextPrime[n, -1]], np= IntegerDigits[ NextPrime[n]]}, And@@PrimeQ[{FromDigits[ Join[np, idn]], FromDigits[Join[idn, pp]], FromDigits[Join[np, idn, pp]]}]]; Select[ Range[300000], ccatQ] (* Harvey P. Dale, Sep 09 2011 *)

CROSSREFS

Cf. A034808-A034821.

Sequence in context: A135418 A309963 A289290 * A210091 A068260 A252365

Adjacent sequences: A034815 A034816 A034817 * A034819 A034820 A034821

KEYWORD

nonn,base

AUTHOR

Patrick De Geest, Oct 15 1998

STATUS

approved

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Last modified December 6 08:36 EST 2022. Contains 358605 sequences. (Running on oeis4.)