A025637 Exponent of 2 (value of i) in n-th number of form 2^i*7^j.

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

Offset

1,3

Links

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

Formula

a(n) = A007814(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, 2]; seq[10^7] (* Amiram Eldar, Nov 08 2025 *)

Crossrefs

Cf. A003591, A007814, A025664.

Sequence in context: A161162 A211000 A025636 * A195826 A331478 A378500

Adjacent sequences: A025634 A025635 A025636 * A025638 A025639 A025640

Keyword

nonn,easy

Author

David W. Wilson

Status

approved