OFFSET
1,1
REFERENCES
Letter from Gary W. Adamson concerning Prouhet-Thue-Morse sequence, Nov. 11, 1999.
LINKS
FORMULA
a(n)=27*n-a(n-1) for n>0, a(0)=9. [Vincenzo Librandi, Aug 06 2010]
G.f. 9*x*( 1+x+x^2 ) / ( (1+x)*(x-1)^2 ). - R. J. Mathar, Sep 18 2013
MATHEMATICA
LinearRecurrence[{1, 1, -1}, {9, 18, 36}, 60] (* Harvey P. Dale, Mar 09 2022 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved