A110359 a(n) = n+1 if n+1 is a prime else a(n) = 2n+1 if 2n+1 is a prime else a(n) = 2*(2n+1) +1 =g(n) if this number is prime else the next candidate is 2*g(n) + 1 etc.

2, 3, 7, 5, 11, 7, 31, 17, 19, 11, 23, 13, 223, 29, 31, 17, 71, 19, 79, 41, 43, 23, 47, 199, 103, 53, 223, 29, 59, 31, 127, 131, 67, 139, 71, 37, 151, 311, 79, 41, 83, 43, 738197503, 89, 367, 47, 191, 97, 199, 101, 103, 53, 107, 109, 223, 113, 463, 59, 239, 61, 991, 251

Offset

1,1

Comments

Subsidiary sequence: number of steps to reach a prime.

a(73) takes more than 2000 iterations, if it exists. - Joshua Zucker, May 08 2006

Links

Table of n, a(n) for n=1..62.

Example

a(13) = 223, 13+1 = 14 is composite, 13*2 +1 = 27 is composite, 27*2 +1 = 55, 55*2 +1 =111 and finally 111*2 +1 = 223 is a prime.

Crossrefs

Sequence in context: A034694 A050921 A087386 * A092977 A057218 A087387

Adjacent sequences: A110356 A110357 A110358 * A110360 A110361 A110362

Keyword

easy,nonn

Author

Amarnath Murthy, Jul 23 2005

Extensions

More terms from Joshua Zucker, May 08 2006

Status

approved