|
| |
|
|
A083647
|
|
For primes p: Number of steps to reach 2 when iterating f(p) = greatest prime divisor of p-1.
|
|
2
| |
|
|
0, 1, 1, 2, 2, 2, 1, 2, 3, 3, 2, 2, 2, 3, 4, 3, 4, 2, 3, 3, 2, 3, 3, 3, 2, 2, 2, 4, 2, 3, 3, 3, 2, 4, 3, 2, 3, 2, 4, 4, 4, 2, 3, 2, 3, 3, 3, 3, 4, 3, 4, 2, 2, 2, 1, 4, 4, 2, 4, 3, 5, 3, 2, 3, 3, 4, 3, 3, 5, 4, 3, 5, 3, 3, 3, 4, 3, 3, 2, 2, 3, 3, 4, 2, 3, 2, 3, 3, 4, 3, 5, 3, 2, 3, 4, 3, 4, 3, 4, 2, 3, 5, 4, 4, 3
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 1,4
|
|
|
COMMENTS
| For smallest prime that requires n steps to reach 2 cf. A082449.
|
|
|
EXAMPLE
| 59 is the 17th prime and takes four steps to reach 2 (59 -> 29 -> 7 ->3 -> 2), so a(17) = 4.
|
|
|
PROG
| (PARI) {forprime(p=2, 571, q=p; c=0; while(q>2, fac=factor(q-1); q=fac[matsize(fac)[1], 1]; c++); print1(c, ", "))}
|
|
|
CROSSREFS
| Cf. A006530, A023503, A082449.
Sequence in context: A000177 A162545 A162544 * A056691 A205011 A130790
Adjacent sequences: A083644 A083645 A083646 * A083648 A083649 A083650
|
|
|
KEYWORD
| nonn
|
|
|
AUTHOR
| Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), May 01 2003
|
| |
|
|
