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A027059 a(n) = A027052(n, 2n-3). 2
0, 2, 6, 18, 52, 146, 406, 1126, 3124, 8684, 24202, 67640, 189576, 532786, 1501254, 4240550, 12005780, 34063896, 96844082, 275848044, 787104288, 2249633916, 6439678858, 18460717684, 52994100984, 152323413890, 438363476086 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,2

LINKS

G. C. Greubel, Table of n, a(n) for n = 2..750

FORMULA

Conjecture D-finite with recurrence (n+1)*a(n) +2*(-4*n-1)*a(n-1) +(19*n-5)*a(n-2) +6*(-n-5)*a(n-3) +3*(-7*n+41)*a(n-4) +2*(4*n-29)*a(n-5) +(n+1)*a(n-6) +6*(n-5)*a(n-7)=0. - R. J. Mathar, Jun 15 2020

MAPLE

T:= proc(n, k) option remember;

      if k<0 or k>2*n then 0

    elif k=0 or k=2 or k=2*n then 1

    elif k=1 then 0

    else add(T(n-1, k-j), j=1..3)

      fi

    end:

seq( T(n, 2*n-3), n=2..30); # G. C. Greubel, Nov 06 2019

MATHEMATICA

T[n_, k_]:= T[n, k]= If[k<0 || k>2*n, 0, If[k==0 || k==2 || k==2*n, 1, If[k==1, 0, Sum[T[n-1, k-j], {j, 3}]]]]; Table[T[n, 2*n-3], {n, 2, 30}] (* G. C. Greubel, Nov 06 2019 *)

PROG

(Sage)

@CachedFunction

def T(n, k):

    if (k<0 or k>2*n): return 0

    elif (k==0 or k==2 or k==2*n): return 1

    elif (k==1): return 0

    else: return sum(T(n-1, k-j) for j in (1..3))

[T(n, 2*n-3) for n in (2..30)] # G. C. Greubel, Nov 06 2019

CROSSREFS

Sequence in context: A245285 A128104 A318570 * A078484 A156989 A077935

Adjacent sequences:  A027056 A027057 A027058 * A027060 A027061 A027062

KEYWORD

nonn

AUTHOR

Clark Kimberling

STATUS

approved

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Last modified August 4 16:34 EDT 2020. Contains 336202 sequences. (Running on oeis4.)