OFFSET
0,5
LINKS
F. T. Adams-Watters, F. Ruskey, Generating Functions for the Digital Sum and Other Digit Counting Sequences, JIS 12 (2009) 09.5.6
FORMULA
Recurrence relation: a(0) = 0, a(3m) = a(m), a(3m+1) = a(3m+2) = 1+a(m).
G.f.: (1/(1-z))*Sum_{m>=1} (z^(3^(m-1)) - z^(3^m))/(1 - z^(3^m)).
Morphism: 0, j -> j,j+1,j+1; e.g., 0 -> 011 -> 011122122 -> ...
MATHEMATICA
Join[{0}, Table[IntegerLength[n, 3]-DigitCount[n, 3, 0], {n, 110}]] (* Harvey P. Dale, Jun 21 2015 *)
PROG
(PARI) a(n)=my(d=digits(n, 3)); sum(i=1, #d, !!d[i]) \\ Charles R Greathouse IV, Jan 13 2014
CROSSREFS
KEYWORD
nonn,base,easy
AUTHOR
Frank Ruskey, Jun 05 2009
STATUS
approved