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

Author

David W. Wilson

Keywords

• easy
• nonn

Links

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

Crossrefs

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

Programs

Mathematica

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 *)

Formula

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