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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 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.)