A025634 Numbers of form 8^i*10^j, with i, j >= 0.

1, 8, 10, 64, 80, 100, 512, 640, 800, 1000, 4096, 5120, 6400, 8000, 10000, 32768, 40960, 51200, 64000, 80000, 100000, 262144, 327680, 409600, 512000, 640000, 800000, 1000000, 2097152, 2621440, 3276800, 4096000, 5120000, 6400000, 8000000

Offset: 1

Author

David W. Wilson

Keywords

• easy
• nonn

Links

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

Crossrefs

Subsequence of A025612.

Programs

Mathematica

n = 10^6; Flatten[Table[8^i*10^j, {i, 0, Log[8, n]}, {j, 0, Log10[n/8^i]}]] // Sort (* Amiram Eldar, Sep 26 2020 *)

PARI

list(lim)=my(v=List(), N); for(n=0, logint(lim\=1, 10), N=10^n; while(N<=lim, listput(v, N); N<<=3)); Set(v) \\ Charles R Greathouse IV, Jan 10 2018

Formula

Sum_{n>=1} 1/a(n) = (8*10)/((8-1)*(10-1)) = 80/63. - Amiram Eldar, Sep 26 2020

a(n) ~ exp(sqrt(2*log(8)*log(10)*n)) / sqrt(80). - Vaclav Kotesovec, Sep 26 2020

a(n) = 8^A025677(n) *10^A025690(n). - R. J. Mathar, Jul 06 2025