A025672 Exponent of 8 (value of j) in n-th number of form 3^i*8^j.

0, 0, 1, 0, 1, 0, 2, 1, 0, 2, 1, 0, 3, 2, 1, 0, 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, 6, 5, 4, 3, 2, 1, 0, 6, 5, 4, 3, 2, 1, 0, 7, 6, 5, 4, 3, 2, 1, 0, 7, 6, 5, 4, 3, 2, 1, 0, 8, 7, 6, 5, 4, 3, 2, 1, 0, 8, 7, 6, 5, 4, 3, 2, 1, 0, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0, 9, 8, 7, 6, 5, 4, 3, 2

Offset

1,7

Links

Sean A. Irvine, Table of n, a(n) for n = 1..10000

Sean A. Irvine, Table of n, a(n) for n = 1..981730 [a large file]

OEIS server, Scatterplot of n, a(n) with n=1..10^6.

Formula

a(n) = valuation(A025615(n),8) = valuation(A025615(n),2)/3 = A007814(A025615(n))/3. - M. F. Hasler, Feb 20 2012

a(n) = A244413(A025615(n)). - Amiram Eldar, Nov 08 2025

Mathematica

seq[lim_] := IntegerExponent[Flatten[Table[3^i*8^j, {i, 0, Log[3, lim]}, {j, 0, Log[8, lim/3^i]}]] // Sort, 8]; seq[10^9] (* Amiram Eldar, Nov 08 2025 *)

Prog

(PARI) A025672(n)=valuation(A025615(n), 8) \\ M. F. Hasler, Feb 20 2012
(PARI) for(n=1, 1e9, n==8^valuation(n, 8)*3^valuation(n, 3)&&print1(valuation(n, 8), ", ")) \\ M. F. Hasler, Feb 20 2012

Crossrefs

Cf. A025615, A025643, A244413.

Sequence in context: A389790 A330759 A216607 * A025665 A357022 A025841

Adjacent sequences: A025669 A025670 A025671 * A025673 A025674 A025675

Keyword

nonn,easy

Author

David W. Wilson

Extensions

Incorrect formula deleted by Sean A. Irvine, Feb 20 2012

Status

approved