OFFSET
1,1
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..1000
Index entries for linear recurrences with constant coefficients, signature (4,0,1,-4).
FORMULA
G.f.: x*(2+x^2) / ( (x-1)*(4*x-1)*(1 + x + x^2) ). - R. J. Mathar, Nov 21 2011
a(n) = 4*a(n-1) + a(n-3) - 4*a(n-4). - Vincenzo Librandi, Jun 22 2012
MATHEMATICA
LinearRecurrence[{4, 0, 1, -4}, {2, 8, 33, 134}, 40] (* Vincenzo Librandi, Jun 22 2012 *)
Module[{nn=30, c}, c=PadRight[{}, nn, {2, 0, 1}]; Table[FromDigits[Take[c, n], 4], {n, nn}]] (* Harvey P. Dale, May 28 2014 *)
PROG
(Magma) I:=[2, 8, 33, 134]; [n le 4 select I[n] else 4*Self(n-1)+Self(n-3)-4*Self(n-4): n in [1..30]]; // Vincenzo Librandi, Jun 22 2012
(PARI) x='x+O('x^99); Vec(x*(2+x^2)/((x-1)*(4*x-1)*(1+x+x^2))) \\ Altug Alkan, Sep 21 2018
CROSSREFS
KEYWORD
nonn,base,easy
AUTHOR
STATUS
approved