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A181657 Generalized (conditional) Riordan array with k-th column generated by x^k * (1 + x - x^2 + x^3)/(1 - 2x^2 - x^4) if k mod 2 = 0, x^k * (1+x)/(1 - 2x^2 - x^4)) otherwise. 2
1, 1, 1, 1, 1, 1, 3, 2, 1, 1, 3, 2, 1, 1, 1, 7, 5, 3, 2, 1, 1, 7, 5, 3, 2, 1, 1, 1, 17, 12, 7, 5, 3, 2, 1, 1, 17, 12, 7, 5, 3, 2, 1, 1, 1, 41, 29, 17, 12, 7, 5, 3, 2, 1, 1, 41, 29, 17, 12, 7, 5, 3, 2, 1, 1, 1 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

0,7

COMMENTS

An eigentriangle of A181656. Even columns are essentially A001333 doubled. Odd columns are doubled Pell numbers (A000129).

Row sums are A181658.

LINKS

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

EXAMPLE

Triangle begins

   1;

   1,  1;

   1,  1,  1;

   3,  2,  1,  1;

   3,  2,  1,  1,  1;

   7,  5,  3,  2,  1,  1;

   7,  5,  3,  2,  1,  1,  1;

  17, 12,  7,  5,  3,  2,  1,  1;

  17, 12,  7,  5,  3,  2,  1,  1,  1;

  41, 29, 17, 12,  7,  5,  3,  2,  1,  1;

  41, 29, 17, 12,  7,  5,  3,  2,  1,  1,  1;

CROSSREFS

Sequence in context: A083716 A231820 A010268 * A172254 A053542 A087284

Adjacent sequences:  A181654 A181655 A181656 * A181658 A181659 A181660

KEYWORD

easy,nonn,tabl

AUTHOR

Paul Barry, Nov 03 2010

STATUS

approved

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Last modified May 26 19:44 EDT 2019. Contains 323597 sequences. (Running on oeis4.)