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A016203
Expansion of 1/((1-x)(1-2x)(1-8x)).
3
1, 11, 95, 775, 6231, 49911, 399415, 3195575, 25565111, 204521911, 1636177335, 13089422775, 104715390391, 837723139511, 6701785148855, 53614281256375, 428914250182071, 3431314001718711, 27450512014273975
OFFSET
0,2
COMMENTS
4*a(n) is the total number of holes in a certain box fractal (start with 8 boxes, 0 hole) after n iterations. See illustration in link. - Kival Ngaokrajang, Jan 27 2015
FORMULA
a(n) = (4*8^(n+1) - 7*2^(n+1) + 3)/21. - Mitch Harris, Jun 27 2005 - corrected by Yahia Kahloune, May 06 2013
a(0) = 1, a(n) = 8*a(n-1) + 2^(n+1) - 1. - Vincenzo Librandi, Feb 09 2011
MAPLE
a:=n->sum((8^(n-j)-2^(n-j))/6, j=0..n): seq(a(n), n=1..19); # Zerinvary Lajos, Jan 15 2007
PROG
(PARI) Vec(1/((1-x)*(1-2*x)*(1-8*x))+O(x^99)) \\ Charles R Greathouse IV, Sep 26 2012
CROSSREFS
Sequence in context: A115203 A164547 A298925 * A241606 A326349 A318599
KEYWORD
nonn,easy
STATUS
approved