A025659 -id:A025659 - cp's OEIS frontend

A025622 Numbers of form 5^i*6^j, with i, j >= 0.

1, 5, 6, 25, 30, 36, 125, 150, 180, 216, 625, 750, 900, 1080, 1296, 3125, 3750, 4500, 5400, 6480, 7776, 15625, 18750, 22500, 27000, 32400, 38880, 46656, 78125, 93750, 112500, 135000, 162000, 194400, 233280, 279936, 390625, 468750, 562500, 675000

Offset: 1

David W. Wilson

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

Cf. A000351 (subset), A000400 (another subset), A025651 (exponent of 5).

n = 10^6; Flatten[Table[5^i*6^j, {i, 0, Log[5, n]}, {j, 0, Log[6, n/5^i]}]] // Sort (* Amiram Eldar, Sep 25 2020 *)

Sum_{n>=1} 1/a(n) = (5*6)/((5-1)*(6-1)) = 3/2. - Amiram Eldar, Sep 25 2020
a(n) ~ exp(sqrt(2*log(5)*log(6)*n)) / sqrt(30). - Vaclav Kotesovec, Sep 25 2020
a(n) = 5^A025651(n) *6^A025659(n). - R. J. Mathar, Jul 06 2025

A025707 Index of 5^n within sequence of numbers of form 5^i*6^j.

Original entry on oeis.org

1, 2, 4, 7, 11, 16, 22, 29, 37, 46, 55, 65, 76, 88, 101, 115, 130, 146, 163, 181, 199, 218, 238, 259, 281, 304, 328, 353, 379, 406, 433, 461, 490, 520, 551, 583, 616, 650, 685, 721, 757, 794, 832, 871, 911, 952, 994, 1037, 1081, 1126, 1171, 1217, 1264, 1312, 1361

Offset: 0

David W. Wilson

Positions of zeros in A025659. - R. J. Mathar, Jul 06 2025

Charles R Greathouse IV, Table of n, a(n) for n = 0..10000

a(n)=my(N=1); n+1+sum(i=1, n, logint(N*=5, 6)); \\ Charles R Greathouse IV, Jan 11 2018

first(n)=my(s, N=1/5); vector(n+1, i, s+=logint(N*=5, 6)+1) \\ Charles R Greathouse IV, Jan 11 2018

Offset corrected by Charles R Greathouse IV, Jan 11 2018

cp's OEIS Frontend

A025622 Numbers of form 5^i*6^j, with i, j >= 0.

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