A271894 - OEIS

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A271894

Expansion of (1+x-3*x^2) / ( 1-2*x-4*x^2+6*x^3 ).

1, 3, 7, 20, 50, 138, 356, 964, 2524, 6768, 17848, 47624, 126032, 335472, 889328, 2364352, 6273184, 16667808, 44242240, 117516608, 311995328, 828603648, 2200088960, 5842620544, 15513975040, 41197898496, 109395973888, 290499691520, 771395887616

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OFFSET

0,2

COMMENTS

Sum of all second elements at level n of the TRIP-Stern sequence corresponding to the permutation triple (e,13,23)

LINKS

Table of n, a(n) for n=0..28.

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

Index entries for linear recurrences with constant coefficients, signature (2,4,-6).

FORMULA

a(n) >= 2^n.

MATHEMATICA

CoefficientList[Series[(1+x-3x^2)/(1-2x-4x^2+6x^3), {x, 0, 30}], x] (* or *) LinearRecurrence[{2, 4, -6}, {1, 3, 7}, 30] (* Harvey P. Dale, Jul 14 2024 *)

PROG

(PARI) x='x+O('x^99); Vec((1+x-3*x^2)/(1-2*x-4*x^2+6*x^3)) \\ Altug Alkan, Apr 16 2016

CROSSREFS

Cf. A271486 (maximum at level n).

Sequence in context: A173400 A281971 A230352 * A066315 A339061 A058499

Adjacent sequences: A271891 A271892 A271893 * A271895 A271896 A271897

KEYWORD

nonn,easy

AUTHOR

R. J. Mathar, Apr 16 2016

STATUS

approved