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A025666
Exponent of 7 (value of j) in n-th number of form 4^i*7^j.
1
0, 0, 1, 0, 1, 2, 0, 1, 2, 0, 3, 1, 2, 0, 3, 1, 4, 2, 0, 3, 1, 4, 2, 0, 5, 3, 1, 4, 2, 0, 5, 3, 1, 6, 4, 2, 0, 5, 3, 1, 6, 4, 2, 7, 0, 5, 3, 1, 6, 4, 2, 7, 0, 5, 3, 8, 1, 6, 4, 2, 7, 0, 5, 3, 8, 1, 6, 4, 9, 2, 7, 0, 5, 3, 8, 1, 6, 4, 9, 2, 7, 0, 5, 10, 3, 8, 1, 6, 4, 9, 2, 7, 0, 5, 10, 3, 8, 1, 6, 11, 4, 9, 2, 7, 0, 5
OFFSET
1,6
LINKS
FORMULA
4^A025648(n)*7^a(n) = A025619(n). - Robert Israel, Aug 11 2019
MAPLE
N:= 10^10: # to consider all terms with 4^i*7^j<=N
S:= {seq(seq(4^i*7^j, j=0..floor(log[7](N/4^i))), i=0..floor(log[4](N)))}:
map(padic:-ordp, sort(convert(S, list)), 7); # Robert Israel, Aug 11 2019
CROSSREFS
Sequence in context: A173863 A022337 A025687 * A025679 A071491 A156537
KEYWORD
nonn
STATUS
approved