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A083904
G.f. 1/(1-x) * Sum_{k>=0} 3^k * x^2^(k+1)/(1+x^2^k).
0
0, 1, 0, 4, 3, 1, 0, 13, 12, 10, 9, 4, 3, 1, 0, 40, 39, 37, 36, 31, 30, 28, 27, 13, 12, 10, 9, 4, 3, 1, 0, 121, 120, 118, 117, 112, 111, 109, 108, 94, 93, 91, 90, 85, 84, 82, 81, 40, 39, 37, 36, 31, 30, 28, 27, 13, 12, 10, 9, 4, 3, 1, 0, 364, 363, 361, 360
OFFSET
1,4
COMMENTS
Distance to next number of form 2^k-1, written down in binary, then interpreted as ternary. Thus the numbers have no 2 in ternary representation.
FORMULA
a(1)=0, a(2n) = 3a(n)+1, a(2n+1) = 3a(n).
a(n) = (1/2)*(3^(floor(log_2(n))+1)-1) - A005836(n).
PROG
(PARI) for(n=1, 100, l=ceil(log(n)/log(2)); t=polcoeff(1/(1-x)*sum(k=0, l, 3^k*(x^2^(k+1))/(1+x^2^k)) + O(x^(n+1)), n); print1(t", "))
CROSSREFS
Sequence in context: A136590 A117026 A316656 * A215861 A327366 A327069
KEYWORD
nonn,easy
AUTHOR
Ralf Stephan, Jun 18 2003
STATUS
approved