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 A181654 An eigentriangle of the number triangle A181653. 2
 1, 1, 1, 2, 1, 1, 3, 2, 1, 1, 6, 4, 2, 1, 1, 9, 6, 3, 2, 1, 1, 18, 12, 6, 4, 2, 1, 1, 27, 18, 9, 6, 3, 2, 1, 1, 54, 36, 18, 12, 6, 4, 2, 1, 1, 81, 54, 27, 18, 9, 6, 3, 2, 1, 1, 162, 108, 54, 36, 18, 12, 6, 4, 2, 1, 1 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 0,4 COMMENTS Generalized (conditional) Riordan array with k-th column generated by x^k*if(mod(k,2)=0,(1+x-x^2)/(1-3x^2),(1+x-x^2+x^3)/(1-3x^2)). Row sums are A181655. LINKS 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, 2, 1, 1, 6, 4, 2, 1, 1, 9, 6, 3, 2, 1, 1, 18, 12, 6, 4, 2, 1, 1, 27, 18, 9, 6, 3, 2, 1, 1, 54, 36, 18, 12, 6, 4, 2, 1, 1, 81, 54, 27, 18, 9, 6, 3, 2, 1, 1, 162, 108, 54, 36, 18, 12, 6, 4, 2, 1, 1 CROSSREFS Sequence in context: A049286 A308477 A079216 * A323756 A192710 A316831 Adjacent sequences:  A181651 A181652 A181653 * A181655 A181656 A181657 KEYWORD easy,nonn,tabl AUTHOR Paul Barry, Nov 03 2010 STATUS approved

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Last modified May 10 19:32 EDT 2021. Contains 343780 sequences. (Running on oeis4.)