A034818 Concatenations C1 and C2 and C3 are all prime (see the comment lines).

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

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