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A181651 Eigentriangle of number triangle A070909. 2
1, 1, 1, 2, 1, 1, 3, 1, 1, 1, 6, 2, 2, 1, 1, 9, 3, 3, 1, 1, 1, 18, 6, 6, 2, 2, 1, 1, 27, 9, 9, 3, 3, 1, 1, 1, 54, 18, 18, 6, 6, 2, 2, 1, 1, 81, 27, 27, 9, 9, 3, 3, 1, 1, 1, 162, 54, 54, 18, 18, 6, 6, 2, 2, 1, 1 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

0,4

COMMENTS

First column is (essentially) A038754. Row sums are A068911. Inverse is A181652.

Generalized (conditional) Riordan array with k-th column generated by If(mod(k,2)=0,x^k*((1+x-x^2)/(1-3x^2),(1+x-2x^2-x^3)/(1-3x^2)).

LINKS

Table of n, a(n) for n=0..65.

P. Barry, Invariant number triangles, eigentriangles and Somos-4 sequences, arXiv preprint arXiv:1107.5490, 2011

EXAMPLE

Triangle begins

1,

1, 1,

2, 1, 1,

3, 1, 1, 1,

6, 2, 2, 1, 1,

9, 3, 3, 1, 1, 1,

18, 6, 6, 2, 2, 1, 1,

27, 9, 9, 3, 3, 1, 1, 1,

54, 18, 18, 6, 6, 2, 2, 1, 1,

81, 27, 27, 9, 9, 3, 3, 1, 1, 1,

162, 54, 54, 18, 18, 6, 6, 2, 2, 1, 1

CROSSREFS

Sequence in context: A160182 A195825 A098824 * A124032 A254046 A137457

Adjacent sequences:  A181648 A181649 A181650 * A181652 A181653 A181654

KEYWORD

nonn,tabl

AUTHOR

Paul Barry, Nov 03 2010

STATUS

approved

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Last modified May 13 01:18 EDT 2021. Contains 343829 sequences. (Running on oeis4.)