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 A026638 T(2n,n), T given by A026637. 1
 1, 2, 8, 26, 92, 332, 1220, 4538, 17036, 64412, 244928, 935684, 3588392, 13806704, 53271548, 206040506, 798600332, 3101109164, 12062148368, 46986821516, 183276382472, 715748620424, 2798274135368, 10951009023716, 42895901012792, 168167959150232, 659793819847040 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..1000 FORMULA From Vaclav Kotesovec, Oct 21 2012: (Start) G.f.: 1/(2+x)+3/((2+x)*sqrt(1-4*x))-1 Recurrence: 2*n*a(n) = (7*n-4)*a(n-1) + 2*(2*n-1)*a(n-2) a(n) ~ 2^(2*n+2)/(3*sqrt(Pi*n)) (End) MATHEMATICA CoefficientList[Series[1/(2+x)+3/((2+x)*Sqrt[1-4*x])-1, {x, 0, 20}], x] (* Vaclav Kotesovec, Oct 21 2012 *) PROG (PARI)  x='x+O('x^66); Vec( 1/(2+x)+3/((2+x)*sqrt(1-4*x))-1 ) \\ Joerg Arndt, May 04 2013 CROSSREFS Sequence in context: A053956 A320802 A052543 * A307401 A067855 A301699 Adjacent sequences:  A026635 A026636 A026637 * A026639 A026640 A026641 KEYWORD nonn AUTHOR STATUS approved

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Last modified July 6 11:37 EDT 2022. Contains 355110 sequences. (Running on oeis4.)