A034819 Concatenations C1 and C2 and C3 and C4 are all prime (see the comment lines).

51, 63, 123, 597, 687, 987, 4429, 12237, 18291, 20013, 29953, 31863, 34653, 48023, 52703, 57147, 59337, 62097, 66727, 71733, 81263, 86589, 101211, 105501, 118617, 121397, 134013, 146191, 147151, 155937, 174723, 175797, 179191, 180189, 205287

Offset: 0

Author

Patrick De Geest, Oct 15 1998

Keywords

• nonn
• base

Comments

C1 = 'nextprime(n) followed by n'

C2 = 'n followed by nextprime(n)'

C3 = 'prevprime(n) followed by n'

C4 = 'n followed by prevprime(n)'

Examples

			n=105501 -> next prime is 105503, previous prime is 105499, thus '105503105501' and '105501105503' and '105501105499' and '105499105501' are all four primes.
		

Crossrefs

Cf. A034808-A034821.