A025477 a(n) = exponent of the n-th nontrivial prime power A025475(n).

0, 2, 3, 2, 4, 2, 3, 5, 2, 6, 4, 2, 3, 7, 2, 5, 8, 2, 3, 2, 9, 2, 4, 6, 2, 2, 10, 3, 2, 2, 2, 11, 7, 3, 2, 4, 2, 5, 2, 2, 12, 2, 3, 2, 2, 2, 8, 3, 2, 2, 13, 2, 2, 2, 2, 2, 3, 2, 4, 6, 2, 14, 5, 2, 2, 2, 9, 2, 2, 3, 2, 2, 2, 4, 3, 2, 2, 2, 15, 2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 10, 2, 16, 2, 3, 2, 2, 2, 2, 7, 2, 3, 2

Offset

1,2

Links

Michael De Vlieger, Table of n, a(n) for n = 1..10000

Formula

a(n) = A051903(A025475(n)) = A001222(A025475(n)). - Reinhard Zumkeller, Mar 10 2003

Mathematica

With[{nn = 2^20}, {0}~Join~Map[FactorInteger[#][[1, -1]] &, Select[Union@ Flatten@ Table[a^2*b^3, {b, nn^(1/3)}, {a, Sqrt[nn/b^3]}], PrimePowerQ] ] ] (* Michael De Vlieger, Oct 23 2023 *)

Crossrefs

Cf. A001222, A025475, A051903.

Sequence in context: A368925 A368710 A080771 * A080189 A076399 A360729

Adjacent sequences: A025474 A025475 A025476 * A025478 A025479 A025480

Keyword

easy,nonn

Author

David W. Wilson

Extensions

Edited by N. J. A. Sloane, Jan 17 2009 at the suggestion of R. J. Mathar

Name edited by Michael De Vlieger, Oct 23 2023

Status

approved