OFFSET
0,2
COMMENTS
a(n)/a(n-1) tends to -5.
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (-1,20).
FORMULA
G.f.: (1+6*x)/(1+x-20*x^2).
a(n) = Sum_{k=0..n} A112555(n,k)*4^k.
a(n) = (10*4^n-(-5)^n)/9. - Klaus Brockhaus, Sep 25 2009
E.g.f.: (10*exp(4*x) - exp(-5*x))/9. - G. C. Greubel, Oct 20 2018
MAPLE
seq(coeff(series((1+6*x)/(1+x-20*x^2), x, n+1), x, n), n = 0 .. 25); # Muniru A Asiru, Oct 21 2018
MATHEMATICA
LinearRecurrence[{-1, 20}, {1, 5}, 40] (* G. C. Greubel, Oct 20 2018 *)
PROG
(PARI) vector(40, n, n--; (10*4^n-(-5)^n)/9) \\ G. C. Greubel, Oct 20 2018
(Magma) [(10*4^n-(-5)^n)/9: n in [0..40]]; // G. C. Greubel, Oct 20 2018
(Python) for n in range(0, 30): print(int((10*4**n-(-5)**n)/9), end=', ') # Stefano Spezia, Oct 21 2018
(GAP) a:=[1, 5];; for n in [3..25] do a[n]:=20*a[n-2]-a[n-1]; od; a; # Muniru A Asiru, Oct 21 2018
CROSSREFS
KEYWORD
easy,sign
AUTHOR
Philippe Deléham, Sep 20 2009
STATUS
approved