|
| |
|
|
A091985
|
|
Number of steps required for the initial value p = 10^n to reach 0 in the recurrence p = pi(p).
|
|
0
| |
|
|
1, 4, 6, 8, 9, 10, 11, 12, 12, 13, 14, 15, 15, 16
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 0,2
|
|
|
LINKS
| Andrew Booker, The Nth Prime Page.
|
|
|
FORMULA
| pi(n) = number of primes less than or equal to n. By repeating n=pi(n), n will reach 0 in a finite number of steps.
|
|
|
EXAMPLE
| Pi(100) = 25
Pi(25) = 9
Pi(9) = 4
Pi(4) = 2
Pi(2) = 1
Pi(1) = 0
Total steps to reach 0 = 6. Thus 6 is the 3rd entry in the sequence corresponding to n=2.
|
|
|
PROG
| (PARI) pr10n(n) = { local c; for(x=0, n, y=10^x; c=0; p=y; while(p, p = pi(p); c++); print1(c", ") ) } pi(n) = { local ct; ct=0; forprime(x=1, n, ct++); return(ct) \pi(x) prime count function
|
|
|
CROSSREFS
| Sequence in context: A085049 A019516 A031977 * A091984 A045762 A047748
Adjacent sequences: A091982 A091983 A091984 * A091986 A091987 A091988
|
|
|
KEYWORD
| hard,nonn
|
|
|
AUTHOR
| Cino Hilliard (hillcino368(AT)gmail.com), Mar 16 2004
|
| |
|
|
