A025664 Exponent of 7 (value of j) in n-th number of form 2^i*7^j.

0, 0, 0, 1, 0, 1, 0, 1, 0, 2, 1, 0, 2, 1, 0, 2, 1, 0, 3, 2, 1, 0, 3, 2, 1, 0, 3, 2, 1, 0, 4, 3, 2, 1, 0, 4, 3, 2, 1, 0, 4, 3, 2, 1, 0, 5, 4, 3, 2, 1, 0, 5, 4, 3, 2, 1, 0, 5, 4, 3, 2, 1, 6, 0, 5, 4, 3, 2, 1, 6, 0, 5, 4, 3, 2, 1, 6, 0, 5, 4, 3, 2, 7, 1, 6, 0, 5, 4, 3, 2, 7, 1, 6, 0, 5, 4, 3, 2, 7, 1, 6, 0, 5, 4, 3, 8, 2, 7

Offset

1,10

Links

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

Formula

a(n) = A214411(A003591(n)). - Amiram Eldar, Nov 08 2025

Mathematica

seq[lim_] := IntegerExponent[Flatten[Table[2^i*7^j, {i, 0, Log2[lim]}, {j, 0, Log[7, lim/2^i]}]] // Sort, 7]; seq[10^7] (* Amiram Eldar, Nov 08 2025 *)

Crossrefs

Cf. A003591, A025637, A214411.

Sequence in context: A132798 A080425 A048141 * A025854 A190766 A025857

Adjacent sequences: A025661 A025662 A025663 * A025665 A025666 A025667

Keyword

nonn,easy

Author

David W. Wilson

Status

approved