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A033134
Base-7 digits are, in order, the first n terms of the periodic sequence with initial period 1,1,0.
1
1, 8, 56, 393, 2752, 19264, 134849, 943944, 6607608, 46253257, 323772800, 2266409600, 15864867201, 111054070408, 777378492856, 5441649449993, 38091546149952, 266640823049664, 1866485761347649, 13065400329433544, 91457802306034808, 640204616142243657
OFFSET
1,2
FORMULA
a(n) = 7*a(n-1) + a(n-3) - 7*a(n-4).
a(n) = floor( (28/171)*7^n ). - Tani Akinari, Jul 16 2014
G.f.: x*(1+x) / ((1-x)*(1-7*x)*(1+x+x^2)). - Colin Barker, Dec 24 2015
EXAMPLE
The first six terms have base-7 representations 1, 11, 110, 1101, 11011, 110110.
PROG
(PARI) Vec(x*(1+x)/((1-x)*(1-7*x)*(1+x+x^2)) + O(x^30)) \\ Colin Barker, Dec 24 2015
CROSSREFS
Cf. A033137 (similar in base 10).
Sequence in context: A170689 A003950 A252701 * A126985 A323699 A323700
KEYWORD
nonn,base,easy
STATUS
approved