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 A027261 a(n) = Sum_{k=0..2n} (k+1) * A025177(n, k). 5
 1, 4, 18, 72, 270, 972, 3402, 11664, 39366, 131220, 433026, 1417176, 4605822, 14880348, 47829690, 153055008, 487862838, 1549681956, 4907326194, 15496819560, 48814981614, 153418513644, 481176247338, 1506290861232, 4707158941350, 14686335897012, 45753584909922 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Table of n, a(n) for n=0..26. FORMULA a(n) = 2(n+1)*3^(n-1), for n>1 (conjectured). - Ralf Stephan, Feb 02 2004 From Colin Barker, Jul 28 2012: (Start) Conjecture: a(n) = 6*a(n-1)-9*a(n-2), for n>3. G.f.: (1-9*x^2+18*x^3)/(1-3*x)^2. (End) CROSSREFS Cf. A014915, A064017, A079272. Cf. A006234. Sequence in context: A034352 A358463 A159715 * A290919 A218892 A307566 Adjacent sequences: A027258 A027259 A027260 * A027262 A027263 A027264 KEYWORD nonn AUTHOR Clark Kimberling EXTENSIONS a(1) corrected and more terms from Sean A. Irvine, Oct 26 2019 STATUS approved

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Last modified August 6 15:42 EDT 2024. Contains 374974 sequences. (Running on oeis4.)