OFFSET
2,2
LINKS
Colin Barker, Table of n, a(n) for n = 2..1000
Index entries for linear recurrences with constant coefficients, signature (8,-26,45,-45,26,-8,1).
FORMULA
G.f.: x^2*(1-2*x+41*x^2-49*x^3+44*x^4-26*x^5+8*x^6-x^7)/((1-3*x+x^2)*(1-x)^5). - Ralf Stephan, Apr 24 2004
From G. C. Greubel, Sep 29 2019: (Start)
a(n) = Sum_{j=0..n-2} binomial(2*n-j, j+5), with a(2) = 1 for n >= 2.
a(n) = Fibonacci(2*n+6) - (48 + 47*n + 23*n^2 + 4*n^3 + 4*n^4)/6 for n >= 3. (End)
MAPLE
with(combinat); seq(`if`(n=2, 1, fibonacci(2*n+6) -(48 +47*n +23*n^2 +4*n^3 +4*n^4)/6), n=2..40); # G. C. Greubel, Sep 29 2019
MATHEMATICA
Table[If[n==2, 1, Fibonacci[2*n+6] -(48 +47*n +23*n^2 +4*n^3 +4*n^4)/6], {n, 2, 40}] (* G. C. Greubel, Sep 29 2019 *)
CoefficientList[Series[x^2(1-2x+41x^2-49x^3+44x^4-26x^5+8x^6-x^7)/ ((1-3x+x^2)(1-x)^5), {x, 0, 30}], x] (* or *) LinearRecurrence[{8, -26, 45, -45, 26, -8, 1}, {1, 6, 63, 344, 1383, 4685, 14323, 41119}, 30] (* Harvey P. Dale, Aug 15 2021 *)
PROG
(PARI) Vec(x^2*(x^7-8*x^6+26*x^5-44*x^4+49*x^3-41*x^2+2*x-1)/((x-1)^5* (x^2-3*x+1)) + O(x^40)) \\ Colin Barker, Nov 19 2014
(PARI) vector(40, n, my(m=n+1); if(m==2, 1, fibonacci(2*m+6) -(48 +47*m +23*m^2 +4*m^3 +4*m^4)/6) ) \\ G. C. Greubel, Sep 29 2019
(Magma) [1] cat [Fibonacci(2*n+6) -(48 +47*n +23*n^2 +4*n^3 +4*n^4)/6: n in [3..40]]; // G. C. Greubel, Sep 29 2019
(Sage) [1]+[fibonacci(2*n+6) -(48 +47*n +23*n^2 +4*n^3 +4*n^4)/6 for n in (3..40)] # G. C. Greubel, Sep 29 2019
(GAP) Concatenation([1], List([3..40], n-> Fibonacci(2*n+6) -(48 +47*n +23*n^2 +4*n^3 +4*n^4)/6) ); # G. C. Greubel, Sep 29 2019
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
EXTENSIONS
More terms from Colin Barker, Nov 19 2014
STATUS
approved