A122367 -id:A122367 - cp's OEIS frontend

A081714 a(n) = F(n)*L(n+1) where F=Fibonacci and L=Lucas numbers.

0, 3, 4, 14, 33, 90, 232, 611, 1596, 4182, 10945, 28658, 75024, 196419, 514228, 1346270, 3524577, 9227466, 24157816, 63245987, 165580140, 433494438, 1134903169, 2971215074, 7778742048, 20365011075, 53316291172, 139583862446, 365435296161, 956722026042

Offset: 0

Ralf Stephan, Apr 03 2003

Also convolution of Fibonacci and Lucas numbers.
For n>2, a(n) represents twice the area of the triangle created by the three points (L(n-3), L(n-2)), (L(n-1), L(n)) and (F(n+3), F(n+2)) where L(k)=A000032(k) and F(k)=A000045(k). - J. M. Bergot, May 20 2014
For n>1, a(n) is the remainder when F(n+3)*F(n+4) is divided by F(n+1)*F(n+2). - J. M. Bergot, May 24 2014

Vincenzo Librandi, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (2,2,-1).

Cf. A000045, A000204.

List([0..30], n -> Fibonacci(n)*(Fibonacci(n+2)+Fibonacci(n))); # G. C. Greubel, Jan 07 2019

[Fibonacci(n)*Lucas(n+1): n in [0..30]]; // Vincenzo Librandi, Sep 08 2012

with(combinat): F:=n-> fibonacci(n): L:= n-> F(n+1)+F(n-1):
a:= n-> F(n)*L(n+1): seq(a(n), n=0..30);

Fibonacci[Range[0,50]]*LucasL[Range[0,50]+1] (* Vladimir Joseph Stephan Orlovsky, Mar 17 2011*)

my(x='x+O('x^51));for(n=0,50,print1(polcoeff(serconvol(Ser((1+2*x)/(1-x-x*x)),Ser(x/(1-x-x*x))),n)", "))

a(n)=fibonacci(n)*(fibonacci(n+2)+fibonacci(n))

a(n) = round((-(-1)^n+(2^(-1-n)*((3-sqrt(5))^n*(-1+sqrt(5))+(1+sqrt(5))*(3+sqrt(5))^n))/sqrt(5))) \\ Colin Barker, Sep 28 2016

[fibonacci(n)*(fibonacci(n+2)+fibonacci(n)) for n in (0..30)] # G. C. Greubel, Jan 07 2019

G.f.: x*(3-2*x)/((1+x)*(1-3*x+x^2)).
a(n) = A122367(n) - (-1)^n. - R. J. Mathar, Jul 23 2010
a(n) = (L(n+1)^2 - F(2*n+2))/2 = ( A001254(n+1) - A001906(n+1) )/2. - Gary Detlefs, Nov 28 2010
a(n+1) = - A186679(2*n+1). - Reinhard Zumkeller, Feb 25 2011
a(n) = A035513(1,n-1)*A035513(2,n-1). - R. J. Mathar, Sep 04 2016
a(n)+a(n+1) = A005248(n+1). - R. J. Mathar, Sep 04 2016
a(n) = (-(-1)^n+(2^(-1-n)*((3-sqrt(5))^n*(-1+sqrt(5))+(1+sqrt(5))*(3+sqrt(5))^n)) / sqrt(5)). - Colin Barker, Sep 28 2016

Simpler definition from Michael Somos, Mar 16 2004

A122369 Dimension of 5-variable non-commutative harmonics (twisted derivative). The dimension of the space of non-commutative polynomials in 5 variables which are killed by all symmetric differential operators (where for a monomial w, d_{xi} ( xi w ) = w and d_{xi} ( xj w ) = 0 for i/=j).

Original entry on oeis.org

1, 4, 19, 93, 459, 2273, 11274, 55964, 277924, 1380527, 6858356, 34074280, 169297743, 841173845, 4179517118, 20766807551, 103184684826, 512698227699, 2547469553647, 12657750705603, 62893284231103, 312501512711984, 1552744642741738, 7715214279423070

Offset: 0

Mike Zabrocki, Aug 30 2006

nonn

			a(1) = 4 because x1-x2, x2-x3, x3-x4, x4-x5 are all of degree 1 and are killed by the differential operator d_x1+d_x2+d_x3+d_x4+d_x5.

C. Chevalley, Invariants of finite groups generated by reflections, Amer. J. Math. 77 (1955), 778-782.
M. C. Wolf, Symmetric functions of noncommutative elements, Duke Math. J. 2 (1936), 626-637.

N. Bergeron, C. Reutenauer, M. Rosas and M. Zabrocki, Invariants and Coinvariants of the Symmetric Group in Noncommuting Variables, arXiv:math.CO/0502082 , Canad. J. Math. 60 (2008), no. 2, 266-296

Cf. A055105, A055107, A087903, A074664, A008277, A112340, A122367, A122369, A122370, A122371, A122372.

coeffs(convert(series((1-6*q+11*q^2-6*q^3)/(1-10*q+32*q^2-37*q^3+11*q^4),q,30),`+`)-O(q^30),q);

gf = With[{n = 5}, Sum[n!/(n-d)! q^d/Product[(1 - r q), {r, 1, d}], {d, 0, n}]/Sum[ q^d/Product[(1 - r q), {r, 1, d}], {d, 0, n}]]; CoefficientList[gf + O[q]^22, q] (* Jean-François Alcover, Nov 17 2018 *)

G.f. (1-6*q+11*q^2-6*q^3)/(1-10*q+32*q^2-37*q^3+11*q^4) more generally, sum( n!/(n-d)!*q^d/prod((1-r*q),r=1..d), d=0..n)/sum( q^d/prod((1-r*q),r=1..d), d=0..n) where n=5.

A099496 a(n) = (-1)^n * Fibonacci(2*n+1).

Original entry on oeis.org

1, -2, 5, -13, 34, -89, 233, -610, 1597, -4181, 10946, -28657, 75025, -196418, 514229, -1346269, 3524578, -9227465, 24157817, -63245986, 165580141, -433494437, 1134903170, -2971215073, 7778742049, -20365011074, 53316291173, -139583862445, 365435296162, -956722026041

Offset: 0

Paul Barry, Oct 19 2004

With interpolated zeros, a Chebyshev transform of A056594, which has g.f. 1/(1+x^2). The image of G(x) under the Chebyshev transform is (1/(1+x^2))G(x/(1+x^2)).

a(n) is the ceiling of the inverse fractional error in approximating phi, the golden section, by the ratio of two successive terms in the Fibonacci series. - Adam Helman (helman(AT)san.rr.com), May 09 2010

			a(3) = (-1)^3 * Fibonacci(2 * 3 + 1) = -Fibonacci(7) = -13. - _Indranil Ghosh_, Feb 04 2017

Indranil Ghosh, Table of n, a(n) for n = 0..2386
Tanya Khovanova, Recursive Sequences
Index entries for linear recurrences with constant coefficients, signature (-3,-1).

Cf. A056594, A122367.

[(-1)^n*Fibonacci(2*n+1): n in [0..40]]; // Vincenzo Librandi, Jul 04 2015

seq((-1)^n*combinat:-fibonacci(2*n+1), n=0 .. 100); # Robert Israel, Jul 02 2015

Table[(-1)^n Fibonacci[2 n + 1], {n, 0, 30}] (* Harvey P. Dale, Aug 22 2016 *)

G.f.: (1+x)/(1+3x+x^2).
a(n) = Sum_{k=0..floor(n/2)} binomial(n-k, k)(-1)^k*cos((n-2k)*Pi/2) (with interpolated zeros);
a(n) = Fibonacci(n+1)(-1)^(n/2)(1 + (-1)^n)/2 (with interpolated zeros).
a(n) = -3*a(n-1) - a(n-2), a(0)=1, a(1)=-2. - Philippe Deléham, Nov 03 2008
From Adam Helman (helman(AT)san.rr.com), May 09 2010: (Start)
a(n) = ceiling( phi / (Fibonacci(n+1)/Fibonacci(n) - phi) ).
An exact expression for the inverse fractional error is phi / (Fibonacci(n+1)/Fibonacci(n) - phi) = (phi/sqrt(5)) * ((-1)^n *(phi^2n) - 1). (End)
a(n) = (-1)^n*A122367(n). - R. J. Mathar, Jul 23 2010

A122368 Dimension of 4-variable non-commutative harmonics (twisted derivative). The dimension of the space of non-commutative polynomials in 4 variables which are killed by all symmetric differential operators (where for a monomial w, d_{xi} ( xi w ) = w and d_{xi} ( xj w ) = 0 for i/=j).

Original entry on oeis.org

1, 3, 11, 42, 162, 627, 2430, 9423, 36549, 141777, 549990, 2133594, 8276985, 32109534, 124565121, 483235875, 1874657763, 7272519066, 28212902154, 109448714619, 424593725526, 1647162628047, 6389978382405, 24789187818585

Offset: 1

Mike Zabrocki, Aug 30 2006

nonn

Empirical: a(n) is the sum of the greatest elements over all lexicographically greatest elements in all partitions in the canonical basis of the Temperley-Lieb algebra of order n. - John M. Campbell, Oct 17 2017

			a(1) = 3 because x1-x2, x2-x3, x3-x4 are all of degree 1 and are killed by the differential operator d_x1+d_x2+d_x3+d_x4
For example, the canonical basis of the Temperley-Lieb algebra of order 3 is {{{-3, 1}, {-2, -1}, {2, 3}}, {{-3, 3}, {-2, 2}, {-1, 1}}, {{-3, 3}, {-2, -1}, {1, 2}}, {{-3, -2}, {-1, 1}, {2, 3}}, {{-3, -2}, {-1, 3}, {1, 2}}}, and the lexicographically greatest elements among all partitions in this basis are {2, 3}, {-1, 1}, {1, 2}, {2, 3}, and {1, 2}, with a(3) = 3+1+2+3+2 = 11. - _John M. Campbell_, Oct 17 2017

Michael De Vlieger, Table of n, a(n) for n = 1..1699
Paul Barry, Centered polygon numbers, heptagons and nonagons, and the Robbins numbers, arXiv:2104.01644 [math.CO], 2021.
N. Bergeron, C. Reutenauer, M. Rosas and M. Zabrocki, Invariants and Coinvariants of the Symmetric Group in Noncommuting Variables, arXiv:math/0502082 [math.CO], 2005; Canad. J. Math. 60 (2008), no. 2, 266-296.
C. Chevalley, Invariants of finite groups generated by reflections, Amer. J. Math. 77 (1955), 778-782.
Hanna Mularczyk, Lattice Paths and Pattern-Avoiding Uniquely Sorted Permutations, arXiv:1908.04025 [math.CO], 2019.
M. C. Wolf, Symmetric functions of noncommutative elements, Duke Math. J. 2 (1936), 626-637.
Index entries for linear recurrences with constant coefficients, signature (6,-9,3).

Cf. A055105, A055107, A087903, A074664, A008277, A112340, A122367, A122369, A122370, A122371, A122372.

coeffs(convert(series((1-3*q+2*q^2)/(1-6*q+9*q^2-3*q^3),q,30),`+`)-O(q^30),q);

LinearRecurrence[{6, -9, 3}, {1, 3, 11}, 24] (* Jean-François Alcover, Sep 22 2017 *)

O.g.f.: (1-3*q+2*q^2)/(1-6*q+9*q^2-3*q^3) more generally, sum( n!/(n-d)!*q^d/prod((1-r*q),r=1..d), d=0..n)/sum( q^d/prod((1-r*q),r=1..d), d=0..n) where n=4

A122391 Dimension of 2-variable non-commutative harmonics (Hausdorff derivative). The dimension of the space of non-commutative polynomials in 2 variables which are killed by all symmetric differential operators (where for a monomial w, d_{xi} ( w ) = sum over all subwords of w deleting xi once).

Original entry on oeis.org

1, 1, 1, 3, 6, 12, 24, 48, 96, 192, 384, 768, 1536, 3072, 6144, 12288, 24576, 49152, 98304, 196608, 393216, 786432, 1572864, 3145728, 6291456, 12582912, 25165824, 50331648, 100663296, 201326592, 402653184, 805306368, 1610612736, 3221225472, 6442450944, 12884901888, 25769803776

Offset: 0

Mike Zabrocki, Aug 31 2006

Except for first couple of terms, series agrees with A003945.
a(n) written in base 2: a(0) = 1, a(1) = 1, a(2) = 1, a(n) for n >= 3: 11, 110, 11000, 110000, ..., i.e.: 2 times 1, (n-3) times 0 (see A003953(n-2)). - Jaroslav Krizek, Aug 17 2009
For n>=2, a(n) equals the numbers of words of length n-2 on alphabet {0,1,2} containing no subwords 00, 11 and 22. - Milan Janjic, Jan 31 2015
Also the number of compositions of n whose first or last part is equal to 1, for n >= 1. - Peter Luschny, Jan 29 2024

			a(1) = 1 because x1 - x2 is killed by d_x1 + d_x2.
a(2) = 1 because x1 x2 - x2 x1 is killed by d_x1+d_x2, d_x1^2 + d_x2^2.
a(3) = 3 because x1 x1 x2 - 2 x1 x2 x1 + x2 x1 x1, x1 x2 x2 - 2 x2 x1 x2 + x2 x2 x1, x1 x1 x2 - x1 x2 x1 - x2 x1 x2 + x2 x2 x1 are all killed by d_x1 + d_x2, d_x1^2 + d_x2^2, d_x1 d_x2, d_x1^3 + d_x2^3 and d_x1^2 d_x2 + d_x1 d_x2^2.
From _Peter Luschny_, Jan 29 2024: (Start)
Compositions of n with 1 in the first or the last slot.
 1: [1];
 2: [1, 1];
 3: [1, 1, 1], [1, 2], [2, 1];
 4: [1, 1, 1, 1], [1, 1, 2], [1, 2, 1], [1, 3], [2, 1, 1], [3, 1];
 5: [1, 1, 1, 1, 1], [1, 1, 1, 2], [1, 1, 2, 1], [1, 1, 3], [1, 2, 1, 1], [1, 2, 2], [1, 3, 1], [1, 4], [2, 1, 1, 1], [2, 2, 1], [3, 1, 1], [4, 1].
(End)

C. Reutenauer, Free Lie algebras. London Mathematical Society Monographs. New Series, 7. Oxford Science Publications. The Clarendon Press, Oxford University Press, New York, 1993. xviii+269 pp.

N. Bergeron, C. Reutenauer, M. Rosas, and M. Zabrocki, Invariants and Coinvariants of the Symmetric Group in Noncommuting Variables, arXiv:math/0502082 [math.CO], 2005. See also, Canad. J. Math. 60 (2008), no. 2, 266-296.
C. Chevalley, Invariants of finite groups generated by reflections, Amer. J. Math. 77 (1955), 778-782.
Index entries for linear recurrences with constant coefficients, signature (2).

Cf. A003945, A034008, A122367, A122392, A122393, A122394.

coeffs(convert(series((1-q)*(1-q^2)/(1-2*q),q,20),`+`)-O(q^20),q);

Table[Ceiling[2^(n-2)] + Floor[2^(n-3)], {n,0,30}] (* Martin Grymel, Oct 17 2012 *)

G.f.: (1-q)*(1-q^2)/(1-2*q).
a(n) = 2^n - 2^(n-1) - 2^(n-2) + 2^(n-3) (for n > 2).
a(0) = 1, a(1) = 1, a(2) = 1, a(n) = 3*2^(n-3) for n > 2.
a(n) = 3*2^(n-3) = 2^(n-3) + 2^(n-2) for n >= 3. - Jaroslav Krizek, Aug 17 2009
a(n) = ceiling(2^(n-2)) + floor(2^(n-3)). - Martin Grymel, Oct 17 2012
E.g.f.: (5 + 3*exp(2*x) + 2*x - 2*x^2)/8. - Stefano Spezia, Jan 26 2025

More terms from Michel Marcus, Jan 26 2025

A094865 Expansion of x^3/((1-3x+x^2)(1-5x+5x^2)).

Original entry on oeis.org

0, 0, 0, 1, 8, 43, 196, 820, 3264, 12597, 47652, 177859, 657800, 2417416, 8844448, 32256553, 117378336, 426440955, 1547491404, 5610955132, 20332248992, 73645557469, 266668876540, 965384509651, 3494279574288, 12646311635088, 45764967830976, 165605867248465

Offset: 0

Herbert Kociemba, Jun 15 2004

With a different offset, number of sequences (s(0), s(1), ..., s(2k+1)) such that 0 < s(i) < 10 and |s(i) - s(i-1)| = 1 for i = 1,2,...,2k+1, with s(0) = 1 and s(2n+1) = 8.

Colin Barker, Table of n, a(n) for n = 0..1000
Roger L. Bagula and Gary W. Adamson, Comments on this sequence
László Németh and László Szalay, Sequences Involving Square Zig-Zag Shapes, J. Int. Seq., Vol. 24 (2021), Article 21.5.2.
Index entries for linear recurrences with constant coefficients, signature (8,-21,20,-5).

Cf. A005024 is a truncated version.

CoefficientList[Series[x^3/((1-3x+x^2)(1-5x+5x^2)),{x,0,30}],x] (* or *) LinearRecurrence[{8,-21,20,-5},{0,0,0,1},30] (* Harvey P. Dale, Jun 07 2014 *)

x='x+O('x^66); concat([0,0,0],Vec(x^3/((1-3*x+x^2)*(1-5*x+5*x^2)))) \\ Joerg Arndt, May 01 2013

a(n) = (1/5)*Sum_{r=1..9} sin(r*Pi/10)*sin(4*r*Pi/5)*(2*cos(r*Pi/10))^(2*n+1).
a(n) = 8*a(n-1) - 21*a(n-2) + 20*a(n-3) - 5*a(n-4).
a(n) = A093129(n)/2 - A122367(n)/2. - R. J. Mathar, Jun 24 2011
a(n) = 2^(-2-n)*(-(3-sqrt(5))^n*(-1+sqrt(5)) + (5-sqrt(5))^n*(1+sqrt(5)) - (1+sqrt(5))*(3+sqrt(5))^n + (-1+sqrt(5))*(5+sqrt(5))^n)/sqrt(5). - Colin Barker, Apr 27 2016

Edited by N. J. A. Sloane, Aug 09 2008

A122370 Dimension of 6-variable non-commutative harmonics (twisted derivative). The dimension of the space of non-commutative polynomials in 6 variables which are killed by all symmetric differential operators (where for a monomial w, d_{xi} ( xi w ) = w and d_{xi} ( xj w ) = 0 for i/=j).

Original entry on oeis.org

1, 5, 29, 172, 1026, 6134, 36712, 219847, 1316963, 7890594, 47282065, 283344410, 1698058817, 10176618298, 60990528210, 365532989831, 2190756912988, 13129979193808, 78692862940748, 471636719623539

Offset: 0

Mike Zabrocki, Aug 30 2006

nonn

			a(1) = 5 because x1-x2, x2-x3, x3-x4, x4-x5, x5-x6 are all of degree 1 and are killed by the differential operator d_x1+d_x2+d_x3+d_x4+d_x5+d_x6.

C. Chevalley, Invariants of finite groups generated by reflections, Amer. J. Math. 77 (1955), 778-782.
M. C. Wolf, Symmetric functions of noncommutative elements, Duke Math. J. 2 (1936), 626-637.

N. Bergeron, C. Reutenauer, M. Rosas and M. Zabrocki, Invariants and Coinvariants of the Symmetric Group in Noncommuting Variables, arXiv:math.CO/0502082 , Canad. J. Math. 60 (2008), no. 2, 266-296
Index entries for linear recurrences with constant coefficients, signature (15,-81,192,-189,53)

Cf. A055105, A055107, A087903, A074664, A008277, A112340, A122367, A122368, A122369, A122371, A122372.

coeffs(convert(series((1-10*q+35*q^2-50*q^3+24*q^4)/ (1-15*q+81*q^2 -192*q^3+189*q^4 -53*q^5),q,20), `+`) -O(q^20),q)

LinearRecurrence[{15, -81, 192, -189, 53}, {1, 5, 29, 172, 1026}, 20] (* Jean-François Alcover, Sep 22 2017 *)

o.g.f. (1-10*q+35*q^2-50*q^3+24*q^4) / (1-15*q+81*q^2 -192*q^3+189*q^4 -53*q^5) more generally, sum( n!/(n-d)!*q^d/prod((1-r*q),r=1..d), d=0..n) / sum( q^d/prod((1-r*q),r=1..d), d=0..n) where n=6.

A122371 Dimension of 7-variable non-commutative harmonics (twisted derivative). The dimension of the space of non-commutative polynomials in 7 variables which are killed by all symmetric differential operators (where for a monomial w, d_{xi} ( xi w ) = w and d_{xi} ( xj w ) = 0 for i/=j).

Original entry on oeis.org

1, 6, 41, 285, 1989, 13901, 97215, 680079, 4758408, 33297267, 233014444, 1630701426, 11412409945, 79870754268, 558989013403, 3912210491549, 27380636068267, 191631324294463, 1341190961828143, 9386756237545989

Offset: 0

Mike Zabrocki, Aug 30 2006

nonn

			a(1) = 6 because x1-x2, x2-x3, x3-x4, x4-x5, x5-x6, x6-x7 are all of degree 1 and are killed by the differential operator d_x1+d_x2+d_x3+d_x4+d_x5+d_x6+d_x7.

C. Chevalley, Invariants of finite groups generated by reflections, Amer. J. Math. 77 (1955), 778-782.
M. C. Wolf, Symmetric functions of noncommutative elements, Duke Math. J. 2 (1936), 626-637.

N. Bergeron, C. Reutenauer, M. Rosas and M. Zabrocki, Invariants and Coinvariants of the Symmetric Group in Noncommuting Variables, arXiv:math.CO/0502082 , Canad. J. Math. 60 (2008), no. 2, 266-296.
Index entries for linear recurrences with constant coefficients, signature (21,-170,669,-1314,1157,-309).

Cf. A055105, A055107, A087903, A074664, A008277, A112340, A122367, A122368, A122369, A122370, A122372.

coeffs(convert(series((1-15*q+ 85*q^2-225*q^3+274*q^4-120*q^5) / (1-21*q+170*q^2-669*q^3+1314*q^4-1157*q^5+309*q^6),q,20),`+`)-O(q^20),q);

LinearRecurrence[{21, -170, 669, -1314, 1157, -309}, {1, 6, 41, 285, 1989, 13901}, 20] (* Jean-François Alcover, Sep 22 2017 *)

G.f.: (1-15*q+ 85*q^2-225*q^3+274*q^4-120*q^5) / (1-21*q+170*q^2-669*q^3 +1314*q^4-1157*q^5 +309*q^6) more generally, sum( n!/(n-d)!*q^d/prod((1-r*q),r=1..d), d=0..n)/sum( q^d/prod((1-r*q), r=1..d), d=0..n) where n=7.

A122372 Dimension of 8-variable non-commutative harmonics (twisted derivative). The dimension of the space of non-commutative polynomials in 8 variables which are killed by all symmetric differential operators (where for a monomial w, d_{xi} ( xi w ) = w and d_{xi} ( xj w ) = 0 for i/=j).

Original entry on oeis.org

1, 7, 55, 438, 3498, 27962, 223604, 1788406, 14305102, 114429193, 915366442, 7322521512, 58577537621, 468602617723, 3748697751384, 29988696932490, 239903055854075, 1919175464438065, 15353030007717639, 122821355074655309

Offset: 0

Mike Zabrocki, Aug 30 2006

nonn

			A122371 a(1) = 7 because x1-x2, x2-x3, x3-x4, x4-x5, x5-x6, x6-x7, x7-x8 are all of degree 1 and are killed by the differential operator d_x1+d_x2+d_x3+d_x4+d_x5+d_x6+d_x7.

N. Bergeron, C. Reutenauer, M. Rosas and M. Zabrocki, Invariants and Coinvariants of the Symmetric Group in Noncommuting Variables, arXiv:math/0502082 [math.CO], 2005; Canad. J. Math. 60 (2008), no. 2, 266-296.
C. Chevalley, Invariants of finite groups generated by reflections, Amer. J. Math. 77 (1955), 778-782.
M. C. Wolf, Symmetric functions of noncommutative elements, Duke Math. J. 2 (1936), 626-637.
Index entries for linear recurrences with constant coefficients, signature (28,-316,1845,-5925,10190,-8249,2119).

Cf. A055105, A055107, A087903, A074664, A008277, A112340, A122367, A122368, A122369, A122370, A122371.

coeffs(convert(series((1-21*q+175*q^2-735*q^3+1624*q^4-1764*q^5+720*q^6)/ (1-28*q+316*q^2-1845*q^3+5925*q^4-10190*q^5+8249*q^6-2119*q^7), q,20),`+`)-O(q^20),q);

n = 8; gf = Sum[n!/(n-d)! q^d/Product[(1 - r q), {r, 1, d}], {d, 0, n}]/ Sum[q^d/Product[(1 - r q), {r, 1, d}], {d, 0, n}] + O[q]^20;
CoefficientList[gf, q] (* Jean-François Alcover, Dec 03 2018 *)

G.f.: (1-21*q+175*q^2-735*q^3+1624*q^4-1764*q^5+720*q^6)/ (1-28*q+316*q^2-1845*q^3+5925*q^4-10190*q^5+8249*q^6-2119*q^7) more generally, sum( n!/(n-d)!*q^d/prod((1-r*q),r=1..d), d=0..n) / sum( q^d/prod((1-r*q), r=1..d), d=0..n) where n=8.

A188648 Binomial sums a(n) = Sum_{k=0..n} (binomial(2n-k,k))^2.

Original entry on oeis.org

1, 2, 11, 63, 376, 2317, 14545, 92512, 594169, 3844787, 25027296, 163701327, 1075049011, 7083830648, 46812088751, 310118453573, 2058919125662, 13695571200353, 91254952276859, 608960974528058, 4069232436916151

Offset: 0

Emanuele Munarini, Apr 07 2011

Central coefficients of A172991.

Bisection of A051286 (Whitney number of level n of the lattice of the ideals of the fence of order 2n). - Paul D. Hanna, Apr 07 2011

Seiichi Manyama, Table of n, a(n) for n = 0..1198 (terms 0..121 from Vincenzo Librandi)

Sum_{k=0..n} (binomial(2n-k,k))^b: A122367(n) = A001519(n+1) (b=1), this sequence (b=2).

Cf. A054142, A172991, A051286.

Table[Sum[Binomial[2n-k,k]^2,{k,0,n}],{n,0,20}]
Table[DifferenceRoot[Function[{y, m}, {4 (-m + n)^2 (-1 - 2 m + 2 n)^2 y[m] + (-5 m^2 - 18 m^3 - 17 m^4 + 12 m n + 56 m^2 n + 68 m^3 n - 8 n^2 - 56 m n^2 - 100 m^2 n^2 + 16 n^3 + 64 m n^3 - 16 n^4) y[1 + m] + (1 + m)^2 (-m + 2 n)^2 y[2 + m] == 0, y[0] == 0, y[1] == 1}]][n + 1], {n, 0, 20}] (* Benedict W. J. Irwin, Nov 03 2016 *)

makelist(sum(binomial(2*n-k,k)^2,k,0,n),n,0,20);

{a(n) = sum(k=0, n, binomial(2*n-k, k)^2)} \\ Seiichi Manyama, Jan 13 2019

G.f.: 1/2*(1/sqrt(1-2*sqrt(x)-x-2*x*sqrt(x)+x^2) + 1/sqrt(1+2*sqrt(x)-x+2*x*sqrt(x)+x^2)).
Recurrence: (n-2)*n*(2*n - 1)*(48*n^2 - 192*n + 169)*a(n) = (576*n^5 - 4032*n^4 + 10212*n^3 - 11414*n^2 + 5457*n - 849)*a(n-1) + 5*(2*n - 3)*(48*n^4 - 288*n^3 + 565*n^2 - 399*n + 64)*a(n-2) + (576*n^5 - 4608*n^4 + 13668*n^3 - 18286*n^2 + 10521*n - 1896)*a(n-3) - (n-3)*(n-1)*(2*n - 5)*(48*n^2 - 96*n + 25)*a(n-4). - Vaclav Kotesovec, Mar 02 2014
a(n) ~ phi^(4*n + 2) / (2^(3/2) * 5^(1/4) * sqrt(Pi*n)), where phi = A001622 = (1+sqrt(5))/2 is the golden ratio. - Vaclav Kotesovec, Mar 02 2014, simplified Jan 13 2019
Conjecture: a(n) = hypergeom([-n,-n,n+1,n+1], [1/2,1/2,1], 1/16). - Velin Yanev, Oct 31 2019
a(n) = A051286(2*n). - Mark van Hoeij, Sep 05 2022

cp's OEIS Frontend

A081714 a(n) = F(n)*L(n+1) where F=Fibonacci and L=Lucas numbers.

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A122369 Dimension of 5-variable non-commutative harmonics (twisted derivative). The dimension of the space of non-commutative polynomials in 5 variables which are killed by all symmetric differential operators (where for a monomial w, d_{xi} ( xi w ) = w and d_{xi} ( xj w ) = 0 for i/=j).

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A099496 a(n) = (-1)^n * Fibonacci(2*n+1).

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A122368 Dimension of 4-variable non-commutative harmonics (twisted derivative). The dimension of the space of non-commutative polynomials in 4 variables which are killed by all symmetric differential operators (where for a monomial w, d_{xi} ( xi w ) = w and d_{xi} ( xj w ) = 0 for i/=j).

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A122391 Dimension of 2-variable non-commutative harmonics (Hausdorff derivative). The dimension of the space of non-commutative polynomials in 2 variables which are killed by all symmetric differential operators (where for a monomial w, d_{xi} ( w ) = sum over all subwords of w deleting xi once).

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A094865 Expansion of x^3/((1-3*x+x^2)*(1-5*x+5*x^2)).

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A094865 Expansion of x^3/((1-3x+x^2)(1-5x+5x^2)).