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

Author

Benoit Cloitre, Dec 17 2002

Keywords

• nonn

Crossrefs

Cf. A050412.

Programs

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)