A046423 Numbers requiring 3 steps to reach a prime under the prime factor concatenation procedure.

25, 35, 56, 62, 69, 72, 76, 85, 90, 100, 114, 125, 138, 143, 152, 189, 213, 221, 238, 250, 259, 260, 270, 275, 278, 303, 318, 333, 364, 366, 369, 390, 403, 441, 448, 454, 469, 470, 473, 485, 507, 512, 519, 522, 529, 559, 560, 572, 588, 591, 624, 629, 648

Offset: 1

Author

Patrick De Geest, Jun 15 1998

Keywords

• nonn
• base

Examples

			69 = 3*23 -> 323 = 17*19 -> 1719 = 3*3*191 and 33191 is prime.
		

Links

• Patrick De Geest, Home Primes

Crossrefs

Cf. A037271, A046411.

Extensions

Edited by Charles R Greathouse IV, Apr 28 2010