A025689 Exponent of 10 (value of j) in n-th number of form 7^i*10^j.

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

Offset

1,6

Links

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

Formula

a(n) = A122840(A025632(n)). - Amiram Eldar, Nov 09 2025

Mathematica

seq[lim_] := IntegerExponent[Flatten[Table[7^i*10^j, {i, 0, Log[7, lim]}, {j, 0, Log10[lim/7^i]}]] // Sort, 10]; seq[10^13] (* Amiram Eldar, Nov 09 2025 *)

Crossrefs

Cf. A025632, A025671, A122840.

Sequence in context: A233381 A025680 A025667 * A025650 A025674 A025681

Adjacent sequences: A025686 A025687 A025688 * A025690 A025691 A025692

Keyword

nonn,easy

Author

David W. Wilson

Status

approved