A025678 - OEIS

A025678

Exponent of 9 (value of j) in n-th number of form 2^i*9^j.

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

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OFFSET

1,12

LINKS

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

FORMULA

a(n) = A007949(A025611(n))/2. - Amiram Eldar, Nov 09 2025

MATHEMATICA

seq[lim_] := IntegerExponent[Flatten[Table[2^i*9^j, {i, 0, Log2[lim]}, {j, 0, Log[9, lim/2^i]}]] // Sort, 9]; seq[10^8] (* Amiram Eldar, Nov 09 2025 *)

CROSSREFS

Cf. A007949, A025611, A025638.

Sequence in context: A237451 A215592 A025684 * A073189 A194519 A025855

Adjacent sequences: A025675 A025676 A025677 * A025679 A025680 A025681

KEYWORD

nonn,easy

AUTHOR

David W. Wilson

STATUS

approved