A145325 Least k such that f(n,k) is not a prime, where f(n,1)=2n+1 and f(n,k)=f(f(n,k-1)) for k>=2.

3, 5, 2, 1, 4, 2, 1, 2, 2, 1, 3, 1, 1, 3, 2, 1, 1, 2, 1, 4, 2, 1, 2, 1, 1, 3, 1, 1, 2, 2, 1, 1, 2, 1, 2, 2, 1, 1, 2, 1, 3, 1, 1, 5, 1, 1, 1, 2, 1, 2, 2, 1, 2, 2, 1, 3, 1, 1, 1, 1, 1, 1, 2, 1, 3, 1, 1, 2, 2, 1, 1, 1, 1, 2, 2, 1, 1, 2, 1, 1, 2, 1, 2, 1, 1, 3, 1, 1, 4, 2, 1, 1, 1, 1, 3, 2, 1, 2, 2, 1, 1, 1, 1, 1, 2

Offset

1,1

Links

Table of n, a(n) for n=1..105.

Example

f(1,1)=3, f(1,2)=7, f(1,3)=15, so a(1)=3.
For n=1,2,3,4,5, the first few f's follow:
1: 3,7,15,31,63
2: 5,11,23,47,95
3: 7,15,31,63,127
4: 9,19,39,77,159
5: 11,23,47,95,191

Crossrefs

Cf. A145326, A145327.

Sequence in context: A183206 A197521 A161865 * A282194 A138508 A353712

Adjacent sequences: A145322 A145323 A145324 * A145326 A145327 A145328

Keyword

easy,nonn

Author

Clark Kimberling, Oct 07 2008

Status

approved