A175128 a(n) = the number of natural numbers m with n steps of iterations of {r - (smallest prime divisor of r)} needed to reach 0 starting at r = m .

1, 1, 2, 1, 1, 2, 1, 1, 2, 2, 1, 2, 1, 1, 2, 1, 1, 2, 1, 1, 2, 1, 1, 2, 2, 1, 2, 1, 1, 3

Offset

2,3

Comments

See A055843, A175126 and A175127.

Links

Table of n, a(n) for n=2..31.

Example

Example (a(7)=2): There are two natural numbers 14 and 15 with 7 steps in this iteration. 14-2=12, 12-2=10, 10-2=8, 8-2=6, 6-2=4, 4-2=2, 2-2=0; 15-3=12, 12-2=10, 10-2=8, 8-2=6, 6-2=4, 4-2=2, 2-2=0.

Crossrefs

Sequence in context: A182907 A334745 A323231 * A359307 A205154 A337772

Adjacent sequences: A175125 A175126 A175127 * A175129 A175130 A175131

Keyword

nonn

Author

Jaroslav Krizek, Feb 15 2010

Status

approved