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

Author

Patrick De Geest, Oct 15 1998

Keywords

• nonn
• base

Comments

C1 = 'nextprime(n) followed by n'

C2 = 'n followed by prevprime(n)'

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

Examples

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

Crossrefs

Cf. A034808-A034821.

Programs

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 *)