OFFSET
1,2
LINKS
FORMULA
G.f.: x*(1+x+2*x^2) / ( (x-1)*(4*x-1)*(1+x+x^2) ). - R. J. Mathar, Apr 27 2015
MATHEMATICA
Table[FromDigits[PadRight[{}, n, {1, 1, 2}], 4], {n, 30}] (* or *) LinearRecurrence[ {4, 0, 1, -4}, {1, 5, 22, 89}, 30] (* Harvey P. Dale, Mar 19 2016 *)
PROG
(PARI) a(n)=([0, 1, 0, 0; 0, 0, 1, 0; 0, 0, 0, 1; -4, 1, 0, 4]^(n-1)*[1; 5; 22; 89])[1, 1] \\ Charles R Greathouse IV, Feb 13 2017
CROSSREFS
KEYWORD
nonn,base,easy
AUTHOR
STATUS
approved