A118144 Numbers of prime factors of l, where l is defined in A118534.

0, 0, 1, 0, 2, 2, 2, 2, 1, 3, 2, 2, 2, 2, 1, 1, 2, 2, 3, 2, 1, 3, 2, 4, 2, 3, 3, 3, 3, 3, 2, 3, 4, 2, 3, 2, 1, 2, 2, 1, 2, 3, 4, 4, 3, 2, 1, 2, 4, 4, 1, 2

Offset

1,5

Comments

a(n) = 0 only for n = 1, 2 and 4.

Links

Remi Eismann, Table of n, a(n) for n = 1..10000

Formula

a(n) = numbers of factors of l, largest l such that prime(n+1) = prime(n) + (prime(n) mod l), or 0 if no such l exists.

Example

For a(1), l=0 thus a(1)=0,
for a(3), l=3 thus a(3)=1,
for a(8), l=15=3*5 thus a(8)=2,
for a(24), l=81=3*3*3*3 thus a(24)=4.

Crossrefs

Cf. A118534, A117563, A118123, A117078.

Sequence in context: A192056 A207385 A306242 * A136691 A361199 A231168

Adjacent sequences: A118141 A118142 A118143 * A118145 A118146 A118147

Keyword

nonn

Author

Rémi Eismann and Fabien Sibenaler, May 14 2006, Feb 14 2008

Status

approved