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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 February 27 16:21 EST 2024. Contains 370378 sequences. (Running on oeis4.)