A025642 Exponent of 3 (value of i) in n-th number of form 3^i*7^j.

0, 1, 0, 2, 1, 3, 0, 2, 4, 1, 3, 5, 0, 2, 4, 6, 1, 3, 5, 7, 0, 2, 4, 6, 8, 1, 3, 5, 7, 0, 9, 2, 4, 6, 8, 1, 10, 3, 5, 7, 0, 9, 2, 11, 4, 6, 8, 1, 10, 3, 12, 5, 7, 0, 9, 2, 11, 4, 13, 6, 8, 1, 10, 3, 12, 5, 14, 7, 0, 9, 2, 11, 4, 13, 6, 15, 8, 1, 10, 3, 12, 5, 14, 7, 0, 16, 9, 2, 11, 4, 13, 6, 15, 8, 1, 17, 10

Offset: 1

Author

David W. Wilson

Keywords

• nonn

Links

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

Crossrefs

Cf. A003594.

Programs

Maple

N:= 10^9: # for 3^i * 7^j <= N
R:= sort([seq(seq(3^i*7^j, j=0 .. ilog[7](N/3^i)),i=0..ilog[3](N))]):
map(padic:-ordp,R,3); # Robert Israel, Jun 04 2025