A025639 Exponent of 2 (value of i) in n-th number of form 2^i*10^j.

0, 1, 2, 3, 0, 4, 1, 5, 2, 6, 3, 0, 7, 4, 1, 8, 5, 2, 9, 6, 3, 0, 10, 7, 4, 1, 11, 8, 5, 2, 12, 9, 6, 3, 13, 0, 10, 7, 4, 14, 1, 11, 8, 5, 15, 2, 12, 9, 6, 16, 3, 13, 0, 10, 7, 17, 4, 14, 1, 11, 8, 18, 5, 15, 2, 12, 9, 19, 6, 16, 3, 13, 0, 10, 20, 7, 17, 4, 14, 1, 11, 21, 8, 18, 5, 15, 2, 12, 22, 9, 19

Offset

1,3

Links

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

Formula

a(n) = A007814(A025612(n)/10^A025684(n)). - Amiram Eldar, Nov 08 2025

Mathematica

seq[lim_] := SortBy[Flatten[Table[{i, j}, {i, 0, Log2[lim]}, {j, 0, Log10[lim/2^i]}], 1], 2^#[[1]]*10^#[[2]] &][[;; , 1]]; seq[10^7] (* Amiram Eldar, Nov 08 2025 *)

Crossrefs

Cf. A007814, A025612, A025684.

Sequence in context: A356624 A025638 A215591 * A195827 A246997 A208384

Adjacent sequences: A025636 A025637 A025638 * A025640 A025641 A025642

Keyword

nonn,easy

Author

David W. Wilson

Status

approved