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 A092492 Arises in enumeration of 321-hexagon-avoiding permutations. 6
 0, 0, 0, 0, 0, 1, 5, 19, 68, 240, 839, 2911, 10054, 34641, 119203, 409893, 1408873, 4841373, 16634350, 57149111, 196333312, 674477710, 2317047808, 7959739375, 27343914410, 93933688630, 322686958885, 1108513737048, 3808031504891 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,7 LINKS Colin Barker, Table of n, a(n) for n = 1..1000 Z. Stankova and J. West, Explicit enumeration of 321, hexagon-avoiding permutations, Discrete Math., 280 (2004), 165-189. Index entries for linear recurrences with constant coefficients, signature (6,-11,9,-4,-4,1). FORMULA a(n) = 2*A058094(n-3) - 5*A058094(n-4) + A058094(n-5) for n >= 6. - Emeric Deutsch, Jun 08 2004 From Colin Barker, Aug 21 2019: (Start) G.f.: x^6*(1 - x) / (1 - 6*x + 11*x^2 - 9*x^3 + 4*x^4 + 4*x^5 - x^6). a(n) = 6*a(n-1) - 11*a(n-2) + 9*a(n-3) - 4*a(n-4) - 4*a(n-5) + a(n-6) for n>7. (End) MAPLE b[1]:=1: b[2]:=2: b[3]:=5: b[4]:=14: b[5]:=42: b[6]:=132: for n from 6 to 45 do b[n+1]:=6*b[n]-11*b[n-1]+9*b[n-2]-4*b[n-3]-4*b[n-4]+b[n-5] od: a[1]:=0: a[2]:=0: a[3]:=0: a[4]:=0: a[5]:=0: for n from 6 to 40 do a[n]:=2*b[n-3]-5*b[n-4]+b[n-5] od: seq(a[n], n=1..40); # Emeric Deutsch, Jun 08 2004 PROG (PARI) concat([0, 0, 0, 0, 0], Vec(x^6*(1 - x) / (1 - 6*x + 11*x^2 - 9*x^3 + 4*x^4 + 4*x^5 - x^6) + O(x^30))) \\ Colin Barker, Aug 21 2019 CROSSREFS Cf. A058094, A092489, A092490, A092491. Sequence in context: A114277 A104496 A001435 * A070857 A143954 A047145 Adjacent sequences:  A092489 A092490 A092491 * A092493 A092494 A092495 KEYWORD nonn,easy AUTHOR N. J. A. Sloane, Apr 04 2004 EXTENSIONS More terms from Emeric Deutsch, Jun 08 2004 STATUS approved

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Last modified June 1 18:43 EDT 2020. Contains 334762 sequences. (Running on oeis4.)