cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A099039 Riordan array (1,c(-x)), where c(x) = g.f. of Catalan numbers.

Original entry on oeis.org

1, 0, 1, 0, -1, 1, 0, 2, -2, 1, 0, -5, 5, -3, 1, 0, 14, -14, 9, -4, 1, 0, -42, 42, -28, 14, -5, 1, 0, 132, -132, 90, -48, 20, -6, 1, 0, -429, 429, -297, 165, -75, 27, -7, 1, 0, 1430, -1430, 1001, -572, 275, -110, 35, -8, 1, 0, -4862, 4862, -3432, 2002, -1001, 429, -154, 44, -9, 1, 0, 16796, -16796, 11934, -7072, 3640, -1638
Offset: 0

Views

Author

Paul Barry, Sep 23 2004

Keywords

Comments

Row sums are generalized Catalan numbers A064310. Diagonal sums are 0^n+(-1)^n*A030238(n-2). Inverse is A026729, as number triangle. Columns have g.f. (xc(-x))^k=((sqrt(1+4x)-1)/2)^k.
Triangle T(n,k), 0 <= k <= n, read by rows, given by [0, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, ... ] DELTA [1, 0, 0, 0, 0, 0, 0, 0, 0, 0, ... ] where DELTA is the operator defined in A084938. - Philippe Deléham, May 31 2005

Examples

			Rows begin {1}, {0,1}, {0,-1,1}, {0,2,-2,1}, {0,-5,5,-3,1}, ...
Triangle begins
  1;
  0,    1;
  0,   -1,    1;
  0,    2,   -2,   1;
  0,   -5,    5,  -3,    1;
  0,   14,  -14,   9,   -4,   1;
  0,  -42,   42, -28,   14,  -5,  1;
  0,  132, -132,  90,  -48,  20, -6,  1;
  0, -429,  429, -297, 165, -75, 27, -7, 1;
Production matrix is
  0,  1,
  0, -1,  1,
  0,  1, -1,  1,
  0, -1,  1, -1,  1,
  0,  1, -1,  1, -1,  1,
  0, -1,  1, -1,  1, -1,  1,
  0,  1, -1,  1, -1,  1, -1,  1,
  0, -1,  1, -1,  1, -1,  1, -1,  1,
  0,  1, -1,  1, -1,  1, -1,  1, -1,  1
		

Crossrefs

The three triangles A059365, A106566 and A099039 are the same except for signs and the leading term.
Cf. A106566 (unsigned version), A059365
The following are all versions of (essentially) the same Catalan triangle: A009766, A030237, A033184, A059365, A099039, A106566, A130020, A047072.

Programs

  • Mathematica
    T[n_, k_]:= If[n == 0 && k == 0, 1, If[n == 0 && k > 0, 0, (-1)^(n + k)*Binomial[2*n - k - 1, n - k]*k/n]];  Table[T[n, k], {n, 0, 15}, {k, 0, n}] // Flatten (* G. C. Greubel, Dec 31 2017 *)
  • PARI
    {T(n,k) = if(n == 0 && k == 0, 1, if(n == 0 && k > 0, 0, (-1)^(n + k)*binomial(2*n - k - 1, n - k)*k/n))};
    for(n=0,15, for(k=0,n, print1(T(n,k), ", "))) \\ G. C. Greubel, Dec 31 2017

Formula

T(n, k) = (-1)^(n+k)*binomial(2*n-k-1, n-k)*k/n for 0 <= k <= n with n > 0; T(0, 0) = 1; T(0, k) = 0 if k > 0. - Philippe Deléham, May 31 2005

A064087 Generalized Catalan numbers C(4; n).

Original entry on oeis.org

1, 1, 5, 41, 413, 4641, 55797, 702297, 9137549, 121909457, 1658755685, 22929591433, 321111942781, 4546112358529, 64958195967957, 935566629270201, 13567825195172973, 197957440018622769, 2903721563443327557, 42796201522669935081, 633443408407612143453
Offset: 0

Views

Author

Wolfdieter Lang, Sep 13 2001

Keywords

Comments

a(n+1) = Y_{n}(n+1) = Z_{n} in the Derrida et al. 1992 reference (see A064094) for alpha=4, beta=1 (or alpha=1, beta=4).

Crossrefs

Cf. A064063 (C(3; n)).

Programs

  • Mathematica
    a[0] = 1; a[n_] := Sum[(n - m)*Binomial[n - 1 + m, m]*4^m/n, {m, 0, n - 1}]; Table[a[n], {n, 0, 18}] (* Jean-François Alcover, Jul 09 2013 *)
  • PARI
    a(n) = if(n<0,0,polcoeff(serreverse((x-3*x^2)/(1+x)^2+O(x^(n+1))),n)) /* Ralf Stephan */
    
  • Sage
    def a(n):
        if n==0: return 1
        return hypergeometric([1-n, n], [-n], 4).simplify()
    [a(n) for n in range(24)] # Peter Luschny, Nov 30 2014

Formula

G.f.: (1+4*x*c(4*x)/3)/(1+x/3) = 1/(1-x*c(4*x)) with c(x) g.f. of Catalan numbers A000108.
a(n) = (1/n)*Sum_{m=0..n-1} (n-m)*binomial(n-1+m, m)*(4^m) = ((-1/3)^n)*(1 - 4*Sum_{k=0..n-1} C(k)*(-12)^k), n >= 1, a(0) = 1, with C(n) = A000108(n) (Catalan).
a(n) = Sum_{k=0...n} A059365(n, k)*4^(n-k). - Philippe Deléham, Jan 19 2004
D-finite with recurrence: 3*n*a(n) + (-47*n+72)*a(n-1) + 8*(-2*n+3)*a(n-2) = 0. - R. J. Mathar, Jun 07 2013 [verified by Georg Fischer, Jul 06 2021]
a(n) = hypergeometric([1-n, n], [-n], 4) for n > 0. - Peter Luschny, Nov 30 2014
a(n) ~ 2^(4*n + 2) / (49*sqrt(Pi)*n^(3/2)). - Vaclav Kotesovec, Jun 10 2019

A064088 Generalized Catalan numbers C(5; n).

Original entry on oeis.org

1, 1, 6, 61, 766, 10746, 161376, 2537781, 41260086, 687927166, 11698135396, 202104763026, 3537486504556, 62595852983236, 1117926476207316, 20124876291104421, 364797768048805926, 6652740911381353206, 121975721251036497636, 2247064873245590484966, 41573071647518070152196
Offset: 0

Views

Author

Wolfdieter Lang, Sep 13 2001

Keywords

Comments

a(n+1) = Y_{n}(n+1) = Z_{n}, n >= 0, in the Derrida et al. 1992 reference (see A064094) for alpha=5, beta =1 (or alpha=1, beta=5).

Crossrefs

Cf. A064087 (C(4, n)).

Programs

  • Magma
    R:=PowerSeriesRing(Rationals(), 30); Coefficients(R!( (9-Sqrt(1-20*x))/(2*(x+4)) )); // G. C. Greubel, May 02 2019
    
  • Mathematica
    a[0] = 1; a[n_] := Sum[(n - m)*Binomial[n - 1 + m, m]*5^m/n, {m, 0, n - 1}]; Table[a[n], {n, 0, 17}] (* Jean-François Alcover, Jul 09 2013 *)
    CoefficientList[Series[(9-Sqrt[1-20*x])/(2*(x+4)), {x,0,30}], x] (* G. C. Greubel, May 02 2019 *)
  • PARI
    a(n)=if(n<0,0,polcoeff(serreverse((x-4*x^2)/(1+x)^2 +O(x^(n+1))), n)) /* Ralf Stephan */
    
  • Sage
    ( (9-sqrt(1-20*x))/(2*(x+4)) ).series(x, 30).coefficients(x, sparse=False) # G. C. Greubel, May 02 2019

Formula

G.f.: (1+5*x*c(5*x)/4)/(1+x/4) = 1/(1-x*c(5*x)) with c(x) g.f. of Catalan numbers A000108.
a(n) = Sum_{m=0..n-1} (n-m)*binomial(n-1+m, m)*(5^m)/n, n >= 1, a(0) := 1.
a(n) = (-1/4)^n*(1 - 5*Sum_{k=0..n-1} C(k)*(-20)^k); with C(n)=A000108(n) (Catalan).
a(n) = Sum_{k=0..n} A059365(n, k)*5^(n-k). - Philippe Deléham, Jan 19 2004
From Gary W. Adamson, Jul 18 2011: (Start)
a(n) = upper left term in M^n, M = an infinite square production matrix as follows:
1, 1, 0, 0, 0, 0, ...
5, 5, 5, 0, 0, 0, ...
5, 5, 5, 5, 0, 0, ...
5, 5, 5, 5, 5, 0, ...
5, 5, 5, 5, 5, 5, ...
... (End)
Conjecture: 4*n*a(n) +(-79*n+120)*a(n-1) +10*(-2*n+3)*a(n-2)=0. - R. J. Mathar, Jun 07 2013
a(n) ~ 4^n * 5^(n+1) / (81*sqrt(Pi)*n^(3/2)). - Vaclav Kotesovec, Jun 10 2019

A064089 Generalized Catalan numbers C(6; n).

Original entry on oeis.org

1, 1, 7, 85, 1279, 21517, 387607, 7312789, 142648495, 2853691357, 58226571271, 1207062556261, 25351452769567, 538285926177325, 11535690316148215, 249189167966657845, 5420206822556721295
Offset: 0

Views

Author

Wolfdieter Lang, Sep 13 2001

Keywords

Comments

a(n+1) = Y_{n}(n+1) = Z_{n}, n >= 0, in the Derrida et al. 1992 reference (see A064094) for alpha=6, beta =1 (or alpha=1, beta=6).

Crossrefs

Cf. A064088 (C(5, n)).

Programs

  • Magma
    R:=PowerSeriesRing(Rationals(), 20); Coefficients(R!( (11 -Sqrt(1-24*x))/(2*(x+5)) )); // G. C. Greubel, May 02 2019
    
  • Mathematica
    CoefficientList[Series[(11 -Sqrt[1-24*x])/(2*(x+5)), {x, 0, 20}], x] (* G. C. Greubel, May 02 2019 *)
  • PARI
    a(n)=if(n<0,0,polcoeff(serreverse((x-5*x^2)/(1+x)^2+O(x^(n+1))), n)) /* Ralf Stephan */
    
  • PARI
    my(x='x+O('x^20)); Vec((11 -sqrt(1-24*x))/(2*(x+5))) \\ G. C. Greubel, May 02 2019
    
  • Sage
    ((11 -sqrt(1-24*x))/(2*(x+5))).series(x, 20).coefficients(x, sparse=False) # G. C. Greubel, May 02 2019

Formula

G.f.: (1 + 6*x*c(6*x)/5)/(1+x/5) = 1/(1 - x*c(6*x)) with c(x) g.f. of Catalan numbers A000108.
a(n) = Sum_{m=0..n-1} (n-m)*binomial(n-1+m, m)*(6^m)/n.
a(n) = (-1/5)^n*(1 - 6*Sum_{k=0..n-1} C(k)*(-30)^k ), n >= 1, a(0) := 1; with C(n)=A000108(n) (Catalan).
a(n) = Sum_{k=0..n} A059365(n, k)*6^(n-k). - Philippe Deléham, Jan 19 2004
Conjecture: 5*n*a(n) +(-119*n+180)*a(n-1) +12*(-2*n+3)*a(n-2)=0. - R. J. Mathar, Jun 07 2013
a(n) ~ 2^(3*n + 1) * 3^(n+1) / (121*sqrt(Pi)*n^(3/2)). - Vaclav Kotesovec, Jun 10 2019

A064090 Generalized Catalan numbers C(7; n).

Original entry on oeis.org

1, 1, 8, 113, 1982, 38886, 817062, 17981769, 409186310, 9549411950, 227307541448, 5497312072330, 134696099554276, 3336563455537768, 83419226227330722, 2102274863070771033, 53347639317495439302
Offset: 0

Views

Author

Wolfdieter Lang, Sep 13 2001

Keywords

Comments

a(n+1) = Y_{n}(n+1) = Z_{n}, n >= 0, in the Derrida et al. 1992 reference (see A064094) for alpha=7, beta =1 (or alpha=1, beta=7).

Crossrefs

Cf. A064089 (C(6, n)).

Programs

  • Magma
    R:=PowerSeriesRing(Rationals(), 20); Coefficients(R!( (13-Sqrt(1-28*x))/(2*(x+6)) )); // G. C. Greubel, May 02 2019
    
  • Mathematica
    a[0]=1; a[n_]:= Sum[(n-m)*Binomial[n-1+m, m]*7^m/n, {m, 0, n-1}]; Table[a[n], {n, 0, 16}] (* Jean-François Alcover, Jul 09 2013 *)
    CoefficientList[Series[(13 -Sqrt[1-28*x])/(2*(x+6)), {x, 0, 20}], x] (* G. C. Greubel, May 02 2019 *)
  • PARI
    a(n)=if(n<0,0,polcoeff(serreverse((x-6*x^2)/(1+x)^2 +O(x^(n+1))), n)) /* Ralf Stephan */
    
  • PARI
    my(x='x+O('x^20)); Vec((13-sqrt(1-28*x))/(2*(x+6))) \\ G. C. Greubel, May 02 2019
    
  • Sage
    ((13-sqrt(1-28*x))/(2*(x+6))).series(x, 20).coefficients(x, sparse=False) # G. C. Greubel, May 02 2019

Formula

G.f.: (1+7*x*c(7*x)/6)/(1+x/6) = 1/(1-x*c(7*x)) with c(x) g.f. of Catalan numbers A000108.
a(n) = Sum_{m=0..n-1} (n-m)*binomial(n-1+m, m)*(7^m)/n.
a(n) = (-1/6)^n*(1 - 7*Sum_{k=0..n-1} C(k)*(-42)^k ), n >= 1, a(0) := 1; with C(n)=A000108(n) (Catalan).
a(n) = Sum_{k=0..n} A059365(n, k)*7^(n-k). - Philippe Deléham, Jan 19 2004
Conjecture: 6*n*a(n) +(-167*n+252)*a(n-1) +14*(-2*n+3)*a(n-2)=0. - R. J. Mathar, Jun 07 2013
a(n) ~ 4^n * 7^(n+1) / (169*sqrt(Pi)*n^(3/2)). - Vaclav Kotesovec, Jun 10 2019

A064091 Generalized Catalan numbers C(8; n).

Original entry on oeis.org

1, 1, 9, 145, 2905, 65121, 1563561, 39322929, 1022586105, 27272680705, 741894295369, 20504949587409, 574176887116441, 16254518495907745, 464436319229036265, 13376293681432402545, 387925710986712480825
Offset: 0

Views

Author

Wolfdieter Lang, Sep 13 2001

Keywords

Comments

a(n+1)= Y_{n}(n+1)= Z_{n}, n >= 0, in the Derrida et al. 1992 reference (see A064094) for alpha=8, beta =1 (or alpha=1, beta=8).

Crossrefs

Cf. A064090 (C(7, n)).

Programs

  • Magma
    R:=PowerSeriesRing(Rationals(), 20); Coefficients(R!( (15 - Sqrt(1-32*x))/(2*(x+7)) )); // G. C. Greubel, May 02 2019
    
  • Mathematica
    a[0]=1; a[n_]:= Sum[(n-m)*Binomial[n+m-1, m]*(8^m)/n, {m, 0, n-1}]; Table[a[n], {n, 0, 16}] (* Jean-François Alcover, Jun 21 2013 *)
    Table[FullSimplify[(-1)^(2*n)*2^(3+5*n)*(1/2*(2*n-1))! Hypergeometric2F1[1,1/2+n,2+n,-224]/(Sqrt[Pi]*(n+1)!)],{n,0,20}] (* Vaclav Kotesovec, Aug 13 2013 *)
    CoefficientList[Series[(15 -Sqrt[1-32*x])/(2*(x+7)), {x,0,20}], x] (* G. C. Greubel, May 02 2019 *)
  • PARI
    a(n)=if(n<0,0,polcoeff(serreverse((x-7*x^2)/(1+x)^2+O(x^(n+1))), n)) /* Ralf Stephan */
    
  • PARI
    my(x='x+O('x^20)); Vec((15 -sqrt(1-32*x))/(2*(x+7))) \\ G. C. Greubel, May 02 2019
    
  • Sage
    ((15 -sqrt(1-32*x))/(2*(x+7))).series(x, 20).coefficients(x, sparse=False) # G. C. Greubel, May 02 2019

Formula

G.f.: (1 + 8*x*c(8*x)/7)/(1+x/7) = 1/(1 - x*c(8*x)) with c(x) g.f. of Catalan numbers A000108.
a(n) = Sum_{m=0..n-1} (n-m)*binomial(n-1+m, m)*(8^m)/n.
a(n) = (-1/7)^n*(1 - 8*Sum_{k=0..n-1} C(k)*(-56)^k ), n >= 1, a(0) := 1; with C(n)=A000108(n) (Catalan).
a(n) = Sum_{k=0..n} A059365(n, k)*8^(n-k). - Philippe Deléham, Jan 19 2004
Conjecture: 7*n*a(n) +(-223*n+336)*a(n-1) +16*(-2*n+3)*a(n-2)=0. - R. J. Mathar, Jun 07 2013
a(n) ~ 2^(5*n+3)/(225*sqrt(Pi)*n^(3/2)). - Vaclav Kotesovec, Aug 13 2013

A064092 Generalized Catalan numbers C(9; n).

Original entry on oeis.org

1, 1, 10, 181, 4078, 102826, 2777212, 78571837, 2298558934, 68964092542, 2110472708140, 65620725560578, 2067160250751436, 65833929303952564, 2116166898185821792, 68565914052628406221, 2237022199842087256678
Offset: 0

Views

Author

Wolfdieter Lang, Sep 13 2001

Keywords

Comments

a(n+1) = Y_{n}(n+1) = Z_{n}, n >= 0, in the Derrida et al. 1992 reference (see A064094) for alpha=9, beta =1 (or alpha=1, beta=9).

Crossrefs

Cf. A064091 (C(8, n)).

Programs

  • Magma
    R:=PowerSeriesRing(Rationals(), 20); Coefficients(R!( (17 - Sqrt(1-36*x))/(2*(x+8)) )); // G. C. Greubel, May 02 2019
    
  • Mathematica
    a[0]=1; a[n_]:= Sum[(n-m)*Binomial[n-1+m, m]*9^m/n, {m, 0, n-1}]; Table[a[n], {n, 0, 16}] (* Jean-François Alcover, Jul 09 2013 *)
    CoefficientList[Series[(17 -Sqrt[1-36*x])/(2*(x+8)), {x, 0, 20}], x] (* G. C. Greubel, May 02 2019 *)
  • PARI
    a(n)=if(n<0,0,polcoeff(serreverse((x-8*x^2)/(1+x)^2+O(x^(n+1))), n)) /* Ralf Stephan */
    
  • PARI
    my(x='x+O('x^20)); Vec((17 -sqrt(1-36*x))/(2*(x+8))) \\ G. C. Greubel, May 02 2019
    
  • Sage
    ((17 -sqrt(1-36*x))/(2*(x+8))).series(x, 20).coefficients(x, sparse=False) # G. C. Greubel, May 02 2019

Formula

G.f.: (1 + 9*x*c(9*x)/8)/(1+x/8) = 1/(1 - x*c(9*x)) with c(x) g.f. of Catalan numbers A000108.
a(n) = Sum_{m=0..n-1} (n-m)*binomial(n-1+m, m)*(9^m)/n.
a(n) = (-1/8)^n*(1 - 9*Sum_{k=0..n-1} C(k)*(-72)^k ), n >= 1, a(0) := 1; with C(n)=A000108(n) (Catalan).
a(n) = Sum_{k=0..n} A059365(n, k)*9^(n-k). - Philippe Deléham, Jan 19 2004
Conjecture: 8*n*a(n) +(-287*n+432)*a(n-1) +18*(-2*n+3)*a(n-2)=0. - R. J. Mathar, Jun 07 2013
a(n) ~ 4^n * 9^(n+1) / (289*sqrt(Pi)*n^(3/2)). - Vaclav Kotesovec, Jun 10 2019

A064093 Generalized Catalan numbers C(10; n).

Original entry on oeis.org

1, 1, 11, 221, 5531, 154941, 4649451, 146150061, 4750427771, 158361063581, 5384626548491, 186023930383501, 6511108452179611, 230400987949757821, 8228844334672249131, 296245683962814194541, 10739133812893020645051
Offset: 0

Views

Author

Wolfdieter Lang, Sep 13 2001

Keywords

Comments

a(n+1) = Y_{n}(n+1) = Z_{n}, n >= 0, in the Derrida et al. 1992 reference (see A064094) for alpha=10, beta =1 (or alpha=1, beta=10).
In general, for m>=1, C(m; n) ~ m * (4*m)^n / ((2*m - 1)^2 * sqrt(Pi) * n^(3/2)). - Vaclav Kotesovec, Jun 10 2019

Crossrefs

Cf. A064092 (C(9, n)).

Programs

  • Magma
    R:=PowerSeriesRing(Rationals(), 20); Coefficients(R!( (19 - Sqrt(1-40*x))/(2*(x+9)) )); // G. C. Greubel, May 02 2019
    
  • Mathematica
    CoefficientList[Series[(19 -Sqrt[1-40*x])/(2*(x+9)), {x, 0, 20}], x] (* G. C. Greubel, May 02 2019 *)
  • PARI
    my(x='x+O('x^20)); Vec((19 -sqrt(1-40*x))/(2*(x+9))) \\ G. C. Greubel, May 02 2019
    
  • Sage
    ((19 -sqrt(1-40*x))/(2*(x+9))).series(x, 20).coefficients(x, sparse=False) # G. C. Greubel, May 02 2019

Formula

G.f.: (1 + 10*x*c(10*x)/9)/(1+x/9) = 1/(1 - x*c(10*x)) with c(x) g.f. of Catalan numbers A000108.
a(n) = Sum_{m=0..n-1} (n-m)*binomial(n-1+m, m)*(10^m)/n.
a(n) = (-1/9)^n*(1 - 10*Sum_{k=0..n-1} C(k)*(-90)^k ), n >= 1, a(0) := 1; with C(n)=A000108(n) (Catalan).
a(n) = Sum_{k=0..n} A059365(n, k)*10^(n-k). - Philippe Deléham, Jan 19 2004
a(n) ~ 2^(3*n + 1) * 5^(n+1) / (361*sqrt(Pi)*n^(3/2)). - Vaclav Kotesovec, Jun 10 2019

A090749 a(n) = 12 * C(2n+1,n-5) / (n+7).

Original entry on oeis.org

1, 12, 90, 544, 2907, 14364, 67298, 303600, 1332045, 5722860, 24192090, 100975680, 417225900, 1709984304, 6962078952, 28192122176, 113649492522, 456442180920, 1827459250276, 7297426411968, 29075683360185, 115631433392020, 459124809056550, 1820529677650320, 7210477496434485
Offset: 5

Views

Author

Philippe Deléham, Feb 15 2004

Keywords

Comments

Also a diagonal of A059365 and A009766. See also A000108, A002057, A003517, A003518, A003519.
Number of standard tableaux of shape (n+6,n-5). - Emeric Deutsch, May 30 2004

Crossrefs

Programs

  • Mathematica
    Table[12*Binomial[2*n + 1, n - 5]/(n + 7), {n,5,50}] (* G. C. Greubel, Feb 07 2017 *)
  • PARI
    for(n=5,50, print1(12*binomial(2*n+1,n-5)/(n+7), ", ")) \\ G. C. Greubel, Feb 07 2017

Formula

a(n) = A039598(n, 5) = A033184(n+7, 12).
G.f.: x^5*C(x)^12 with C(x) g.f. of A000108(Catalan).
Let A be the Toeplitz matrix of order n defined by: A[i,i-1]=-1, A[i,j]=Catalan(j-i), (i<=j), and A[i,j]=0, otherwise. Then, for n>=11, a(n-6)=(-1)^(n-11)*coeff(charpoly(A,x),x^11). - Milan Janjic, Jul 08 2010
a(n) = A214292(2*n,n-6) for n > 5. - Reinhard Zumkeller, Jul 12 2012
From Karol A. Penson, Nov 21 2016: (Start)
O.g.f.: z^5 * 4^6/(1+sqrt(1-4*z))^12.
Recurrence: (-4*(n-5)^2-58*n+80)*a(n+1)-(-n^2-6*n+27)*a(n+2)=0, a(0),a(1),a(2),a(3),a(4)=0,a(5)=1,a(6)=12, n>=5.
Asymptotics: (-903+24*n)*4^n*sqrt(1/n)/(sqrt(Pi)*n^2).
Integral representation as n-th moment of a signed function W(x) on x=(0,4),in Maple notation: a(n+5)=int(x^n*W(x),x=0..4),n=0,1,..., where W(x)=(256/231)*sqrt(4-x)*JacobiP(5, 1/2, 1/2, (1/2)*x-1)*x^(11/2)/Pi and JacobiP are Jacobi polynomials. Note that W(0)=W(4)=0. (End).
From Ilya Gutkovskiy, Nov 21 2016: (Start)
E.g.f.: 6*exp(2*x)*BesselI(6,2*x)/x.
a(n) ~ 3*2^(2*n+3)/(sqrt(Pi)*n^(3/2)). (End)
From Amiram Eldar, Sep 26 2022: (Start)
Sum_{n>=5} 1/a(n) = 88699/15120 - 71*Pi/(27*sqrt(3)).
Sum_{n>=5} (-1)^(n+1)/a(n) = 102638*log(phi)/(75*sqrt(5)) - 22194839/75600, where phi is the golden ratio (A001622). (End)

Extensions

Missing term 113649492522 inserted by Ilya Gutkovskiy, Dec 07 2016
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