login
A271898
Expansion of ( 1+x^2 ) / ( 1-4*x+5*x^2-4*x^3 ).
2
1, 4, 12, 32, 84, 224, 604, 1632, 4404, 11872, 31996, 86240, 232468, 626656, 1689244, 4553568, 12274676, 33087840, 89192252, 240428512, 648104148, 1747043040, 4709365468, 12694663264, 34219997876, 92244137056, 248655211900, 670280153824, 1806821104020, 4870504494560, 13129033073436
OFFSET
0,2
COMMENTS
Sum of all third elements at level n of the TRIP-Stern sequence corresponding to the permutation triple (e,e,e)
LINKS
Ilya Amburg, Krishna Dasaratha, Laure Flapan, Thomas Garrity, Chansoo Lee, Cornelia Mihaila, Nicholas Neumann-Chun, Sarah Peluse, Matthew Stoffregen, Stern Sequences for a Family of Multidimensional Continued Fractions: TRIP-Stern Sequences, arXiv:1509.05239 [math.CO], 2015, Section 7.2.1
MATHEMATICA
CoefficientList[Series[(1+x^2)/(1-4*x+5*x^2-4*x^3), {x, 0, 40}], x] (* or *) LinearRecurrence[{4, -5, 4}, {1, 4, 12}, 40] (* Harvey P. Dale, Apr 20 2016 *)
PROG
(PARI) x='x+O('x^99); Vec((1+x^2)/(1-4*x+5*x^2-4*x^3)) \\ Altug Alkan, Apr 16 2016
CROSSREFS
Cf. A000930 (maximum at level n).
Sequence in context: A135248 A205976 A291038 * A276178 A120369 A001665
KEYWORD
nonn,easy
AUTHOR
R. J. Mathar, Apr 16 2016
STATUS
approved