A078681 Start with n; iterate the process x -> ceiling(3x/2) until reach a prime. Sequence gives number of steps to reach a prime or 0 if no prime is ever reached.

1, 1, 1, 53, 5, 52, 1, 4, 51, 2, 1, 3, 39, 50, 1, 162, 3, 2, 1, 38, 49, 4, 2, 161, 50, 2, 1, 52, 4, 37, 1, 48, 3, 13, 1, 160, 9, 49, 1, 8, 42, 51, 18, 3, 36, 8, 1, 47, 3, 2, 12, 35, 27, 159, 1, 8, 48, 2, 1, 7, 4, 41, 50, 16, 17, 2, 1, 35, 7, 13, 1, 46, 11, 2, 1, 3, 11, 34, 2, 26, 158, 7, 6, 7

Offset

1,4

Links

Table of n, a(n) for n=1..84.

Prog

(PARI) a(n)=if(n<0, 0, s=n; c=1; while(isprime(ceil(3*s/2))==0, s=ceil(3*s/2); c++); c)

Crossrefs

Cf. A050412.

Sequence in context: A198776 A051320 A232126 * A143294 A143428 A143385

Adjacent sequences: A078678 A078679 A078680 * A078682 A078683 A078684

Keyword

nonn

Author

Benoit Cloitre, Dec 17 2002

Status

approved