A025669 Exponent of 7 (value of i) in n-th number of form 7^i*8^j.

0, 1, 0, 2, 1, 0, 3, 2, 1, 0, 4, 3, 2, 1, 0, 5, 4, 3, 2, 1, 0, 6, 5, 4, 3, 2, 1, 0, 7, 6, 5, 4, 3, 2, 1, 0, 8, 7, 6, 5, 4, 3, 2, 1, 0, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3

Offset

1,4

Links

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

Formula

a(n) = A214411(A036566(n)). - Amiram Eldar, Nov 08 2025

Mathematica

seq[lim_] := IntegerExponent[Flatten[Table[7^i*8^j, {i, 0, Log[7, lim]}, {j, 0, Log[8, lim/7^i]}]] // Sort, 7]; seq[10^13] (* Amiram Eldar, Nov 08 2025 *)

Crossrefs

Cf. A025675, A036566, A214411.

Differs from A025581 at a(136).

Sequence in context: A219649 A292160 A025581 * A025676 A025683 A025660

Adjacent sequences: A025666 A025667 A025668 * A025670 A025671 A025672

Keyword

nonn,easy

Author

David W. Wilson

Status

approved