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A046423
Numbers requiring 3 steps to reach a prime under the prime factor concatenation procedure.
0
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
1,1
LINKS
EXAMPLE
69 = 3*23 -> 323 = 17*19 -> 1719 = 3*3*191 and 33191 is prime.
CROSSREFS
Sequence in context: A276290 A173251 A063149 * A347612 A331808 A153446
KEYWORD
nonn,base
AUTHOR
Patrick De Geest, Jun 15 1998
EXTENSIONS
Edited by Charles R Greathouse IV, Apr 28 2010
STATUS
approved