OFFSET
1,2
COMMENTS
n and a(n) are of the same parity. Except for the first three terms and a(5)=27, there is no perfect powers (A001597) in the first 225 terms. In fact there is always at least one factor which is represented only once. - Robert G. Wilson v, Aug 27 2003
LINKS
Martin Burtscher, Igor Szczyrba, and RafaĆ Szczyrba, Analytic Representations of the n-anacci Constants and Generalizations Thereof, Journal of Integer Sequences, Vol. 18 (2015), Article 15.4.5.
Index entries for linear recurrences with constant coefficients, signature (1,1,1).
FORMULA
a(n) = a(n-1) + a(n-2) + a(n-3).
From R. J. Mathar, Apr 20 2009: (Start)
G.f.: -x*(1+3*x+4*x^2)/(-1+x+x^2+x^3). (End)
MATHEMATICA
a[1] = 1; a[2] = 4; a[3] = 9; a[n_] := a[n] = a[n - 3] + a[n - 2] + a[n - 1]; Table[ a[n], {n, 1, 30}]
Transpose[NestList[Flatten[{Rest[#], Total[#]}]&, {1, 4, 9}, 40]][[1]] (* Harvey P. Dale, Mar 24 2011 *)
LinearRecurrence[{1, 1, 1}, {1, 4, 9}, 33] (* Ray Chandler, Dec 08 2013 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Jun Mizuki (suzuki32(AT)sanken.osaka-u.ac.jp), Aug 26 2003
EXTENSIONS
More terms from Robert G. Wilson v, Aug 27 2003
STATUS
approved