A081879 Number of steps for convergence (to 1 or 3) for the process in A081878.

0, 1, 0, 2, 4, 1, 6, 3, 6, 5, 8, 2, 5, 7, 5, 4, 7, 7, 10, 6, 10, 9, 7, 3, 7, 6, 9, 8, 6, 6, 9, 5, 9, 8, 9, 8, 8, 11, 8, 7, 11, 11, 9, 10, 9, 8, 9, 4, 9, 8, 8, 7, 10, 10, 10, 9, 8, 7, 11, 7, 7, 10, 7, 6, 11, 10, 11, 9, 11, 10, 10, 9, 13, 9, 13, 12, 10, 9, 13, 8, 13, 12, 11, 12, 11, 10, 12, 11, 10

Offset

1,4

Links

Table of n, a(n) for n=1..89.

Example

For n = 33 we have 34,17,20,10,5,8,4,2,1 = 9 steps.

Prog

(PARI) countprp3(n) = { for(x=1, n, c=0; p1 = x; while(p1>1, if(p1%2==0, p1/=2, if(isprime(p1), p1+=3, p1 = p1+1; )); if(p1==3, break); c++; ); print1(c" ") )
(MIT Scheme) (define (A081879 n) (cond ((or (= 1 n) (= 3 n)) 0) ((even? n) (1+ (A081879 (/ n 2)))) ((isprime? n) (1+ (A081879 (+ n 3)))) (else (1+ (A081879 (1+ n))))))

Crossrefs

Cf. A081878, A006577.

Sequence in context: A360555 A249146 A225679 * A066248 A065164 A138124

Adjacent sequences: A081876 A081877 A081878 * A081880 A081881 A081882

Keyword

easy,nonn

Author

Cino Hilliard, Apr 12 2003

Extensions

Edited by Antti Karttunen and Jud McCranie, Jun 03 2003

Status

approved