A054575 Number of iterations to reach new prime in A054574.

4, 2, 2, 2, 3, 2, 2, 2, 2, 2, 5, 2, 10, 2, 3, 3, 2, 3, 3, 3, 3, 2, 2, 2, 2, 4, 2, 3, 3, 3, 2, 3, 3, 2, 2, 6, 18, 2, 2, 2, 16, 3, 16, 4, 2, 2, 4, 3, 2, 4, 2, 2, 5, 3, 2, 3, 2, 3, 4, 6, 3, 2, 12, 10, 2, 2, 4, 2, 4, 2, 2, 10, 2, 4, 3, 2, 4, 2, 3, 2, 2, 9, 6, 2, 2, 20, 3, 2, 3, 3, 3, 2, 10, 15, 2, 2, 11, 10

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Example

a(5)=3 because beginning at 11, the next prime, 47, is attained in 3 steps.

Mathematica

f[n_] := n + Plus @@ Times @@@ FactorInteger@n; a[n_] := Length[NestWhileList[f, (p = Prime[n]), # == p || CompositeQ[#] &]] - 1; Array[a, 100] (* Amiram Eldar, Sep 07 2019 *)

Crossrefs

Cf. A054574.

Sequence in context: A303577 A010314 A080133 * A129107 A341686 A353636

Adjacent sequences: A054572 A054573 A054574 * A054576 A054577 A054578

Keyword

easy,nonn

Author

Enoch Haga, Apr 11 2000

Status

approved