|
Search: id:A037271
|
|
|
| A037271 |
|
Number of steps to reach a prime under "replace n by concatenation of its prime factors", when applied to n-th composite number, or -1 if no such number. |
|
+0
18
|
|
| 2, 1, 13, 2, 4, 1, 5, 4, 4, 1, 15, 1, 1, 2, 3, 4, 4, 1, 2, 2, 1, 5, 3, 2, 2, 1, 9, 2, 9, 6, 1, 15
(list; graph; listen)
|
|
|
OFFSET
|
1,1
|
|
|
LINKS
|
P. De Geest, Home Primes
Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.
|
|
EXAMPLE
|
Starting with 14 (the seventh composite number) we get 14=2*7, 27=3*3*3, 333=3*3*37, 3337=47*71, 4771=13*367, 13367 is prime; so a(7)=5.
|
|
CROSSREFS
|
Cf. A037271-A037274, A056938.
Adjacent sequences: A037268 A037269 A037270 this_sequence A037272 A037273 A037274
Sequence in context: A009483 A124916 A007418 this_sequence A074955 A064079 A112226
|
|
KEYWORD
|
nonn,nice,base,hard
|
|
AUTHOR
|
Jeff Burch (gburch(AT)erols.com)
|
|
EXTENSIONS
|
Starting with 49, no prime has been reached after 79 steps.
|
|
|
Search completed in 0.002 seconds
|
