A025680 -id:A025680 - cp's OEIS frontend

A025628 Numbers of form 6^i*9^j, with i, j >= 0.

1, 6, 9, 36, 54, 81, 216, 324, 486, 729, 1296, 1944, 2916, 4374, 6561, 7776, 11664, 17496, 26244, 39366, 46656, 59049, 69984, 104976, 157464, 236196, 279936, 354294, 419904, 531441, 629856, 944784, 1417176, 1679616, 2125764, 2519424, 3188646

Offset: 1

David W. Wilson

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

Subsequence of A025614.

n = 10^6; Flatten[Table[6^i*9^j, {i, 0, Log[6, n]}, {j, 0, Log[9, n/6^i]}]] // Sort (* Amiram Eldar, Sep 26 2020 *)

Sum_{n>=1} 1/a(n) = (6*9)/((6-1)*(9-1)) = 27/20. - Amiram Eldar, Sep 26 2020
a(n) ~ exp(sqrt(2*log(6)*log(9)*n)) / sqrt(54). - Vaclav Kotesovec, Sep 26 2020
a(n) = 6^A025662(n) *9^A025680(n). - R. J. Mathar, Jul 06 2025

A025718 Index of 6^n within sequence of numbers of form 6^i*9^j.

Original entry on oeis.org

1, 2, 4, 7, 11, 16, 21, 27, 34, 42, 51, 60, 70, 81, 93, 106, 120, 134, 149, 165, 182, 200, 218, 237, 257, 278, 300, 323, 346, 370, 395, 421, 448, 475, 503, 532, 562, 593, 624, 656, 689, 723, 758, 794, 830, 867, 905, 944, 984, 1024, 1065, 1107, 1150, 1194, 1239, 1284

Offset: 1

David W. Wilson

nonn

Positions of zeros in A025680. - R. J. Mathar, Jul 06 2025

Robert Israel, Table of n, a(n) for n = 1..10000

Cf. A025628.

with(priqueue):
initialize(PQ):
insert([-1,0,0],PQ):
count:= 0: R:= NULL:
for i from 1 while count < 100 do
  v:= extract(PQ);
if v[3] = 0 then R:= R,i; count:= count+1; insert([v[1]*6,v[2]+1,0],PQ);
insert([v[1]*9, v[2], v[3]+1],PQ)
od:
R; # Robert Israel, Jan 21 2024

cp's OEIS Frontend

A025628 Numbers of form 6^i*9^j, with i, j >= 0.

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