login
A163227
Fibonacci-accumulation sequence.
1
1, 1, 1, 2, 2, 4, 3, 7, 5, 12, 8, 20, 13, 33, 21, 54, 34, 88, 55, 143, 89, 232, 144, 376, 233, 609, 377, 986, 610, 1596, 987, 2583, 1597, 4180, 2584, 6764, 4181, 10945, 6765, 17710, 10946, 28656, 17711, 46367, 28657, 75024, 46368, 121392, 75025, 196417
OFFSET
1,4
COMMENTS
Accumulation of A000045 and A000071.
FORMULA
a(n) = 2*a(n-2) - a(n-6), where a(1,2,3)=1.
G.f.: x*(1 + x - x^2)/(1 - 2*x^2 + x^6). - G. C. Greubel, Dec 11 2016
MATHEMATICA
LinearRecurrence[{0, 2, 0, 0, 0, -1}, {1, 1, 1, 2, 2, 4}, 50] (* or *) CoefficientList[Series[x*(1 + x - x^2)/(1 - 2*x^2 + x^6), {x, 1, 50}], x] (* G. C. Greubel, Dec 11 2016 *)
PROG
(PARI) Vec(x*(1 + x - x^2)/(1 - 2*x^2 + x^6) + O(x^50)) \\ G. C. Greubel, Dec 11 2016
(Magma) m:=55; R<x>:=PowerSeriesRing(Integers(), m); Coefficients(R!(x*(1+x-x^2)/(1-2*x^2+x^6))); // Vincenzo Librandi, Dec 12 2016
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Mark Dols, Jul 23 2009
STATUS
approved