A034816 Concatenations C1 and C2 are both prime (see the comment lines).

9, 51, 63, 117, 123, 157, 183, 213, 217, 219, 257, 263, 321, 327, 333, 423, 441, 473, 541, 597, 621, 687, 693, 723, 777, 879, 909, 987, 1101, 1143, 1187, 1387, 1459, 1551, 1887, 2127, 2179, 2193, 2817, 3197, 3339, 3513, 3633, 4029, 4209, 4429, 4529, 4557

Offset: 0

Author

Patrick De Geest, Oct 15 1998

Keywords

• nonn
• base

Comments

C1 = 'prevprime(n) followed by n'

C2 = 'n followed by nextprime(n)'

Examples

			n=1551 -> previous prime is 1549, next prime is 1553, thus '15491551' and '15511553' are both primes.
		

Crossrefs

Cf. A034808-A034821.