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.

Showing 1-10 of 10 results.

A085880 Triangle T(n,k) read by rows: multiply row n of Pascal's triangle (A007318) by the n-th Catalan number (A000108).

Original entry on oeis.org

1, 1, 1, 2, 4, 2, 5, 15, 15, 5, 14, 56, 84, 56, 14, 42, 210, 420, 420, 210, 42, 132, 792, 1980, 2640, 1980, 792, 132, 429, 3003, 9009, 15015, 15015, 9009, 3003, 429, 1430, 11440, 40040, 80080, 100100, 80080, 40040, 11440, 1430, 4862, 43758, 175032, 408408, 612612, 612612, 408408, 175032, 43758, 4862
Offset: 0

Views

Author

N. J. A. Sloane, Aug 17 2003

Keywords

Comments

Coefficients of terms in the series reversion of (1-k*x-(k+1)*x^2)/(1+x). - Paul Barry, May 21 2005
Equals A131427 * A007318 as infinite lower triangular matrices. [Philippe Deléham, Sep 15 2008]
Sum_{k=0..n} T(n,k)*x^k = A168491(n), A000007(n), A000108(n), A151374(n), A005159(n), A151403(n), A156058(n), A156128(n), A156266(n), A156270(n), A156273(n), A156275(n) for x = -2, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 respectively. - Philippe Deléham, Nov 15 2013
Diagonal sums are A052709(n+1). - Philippe Deléham, Nov 15 2013

Examples

			Triangle starts:
[ 1]     1;
[ 2]     1,     1;
[ 3]     2,     4,      2;
[ 4]     5,    15,     15,      5;
[ 5]    14,    56,     84,     56,     14;
[ 6]    42,   210,    420,    420,    210,     42;
[ 7]   132,   792,   1980,   2640,   1980,    792,    132;
[ 8]   429,  3003,   9009,  15015,  15015,   9009,   3003,    429;
[ 9]  1430, 11440,  40040,  80080, 100100,  80080,  40040,  11440,  1430;
[10]  4862, 43758, 175032, 408408, 612612, 612612, 408408, 175032, 43758, 4862;
...
		

Programs

  • GAP
    Flat(List([0..10], n-> List([0..n], k-> Binomial(n,k)*Binomial(2*n,n)/( n+1) ))); # G. C. Greubel, Feb 07 2020
  • Magma
    [Binomial(n,k)*Catalan(n): k in [0..n], n in [0..10]]; // G. C. Greubel, Feb 07 2020
    
  • Maple
    seq(seq(binomial(n, k)*binomial(2*n, n)/(n+1), k = 0..n), n = 0..10); # G. C. Greubel, Feb 07 2020
  • Mathematica
    Table[Binomial[n, k]*CatalanNumber[n], {n,0,10}, {k,0,n}]//Flatten (* G. C. Greubel, Feb 07 2020 *)
  • PARI
    tabl(nn) = {for (n=0, nn, c =  binomial(2*n,n)/(n+1); for (k=0, n, print1(c*binomial(n, k), ", ");); print(););} \\ Michel Marcus, Apr 09 2015
    
  • Sage
    [[binomial(n,k)*catalan_number(n) for k in (0..n)] for n in (0..10)] # G. C. Greubel, Feb 07 2020
    

Formula

Triangle given by [1, 1, 1, 1, 1, 1, ...] DELTA [1, 1, 1, 1, 1, 1, ...] where DELTA is Deléham's operator defined in A084938.
Sum_{k>=0} T(n, k) = A151374(n) (row sums). - Philippe Deléham, Aug 11 2005
G.f.: (1-sqrt(1-4*(x+y)))/(2*(x+y)). - Vladimir Kruchinin, Apr 09 2015

A290605 Square array A(n,k), n>=0, k>=0, read by antidiagonals, where column k is the expansion of 2/(1 + sqrt(1 - 4*k*x)).

Original entry on oeis.org

1, 1, 0, 1, 1, 0, 1, 2, 2, 0, 1, 3, 8, 5, 0, 1, 4, 18, 40, 14, 0, 1, 5, 32, 135, 224, 42, 0, 1, 6, 50, 320, 1134, 1344, 132, 0, 1, 7, 72, 625, 3584, 10206, 8448, 429, 0, 1, 8, 98, 1080, 8750, 43008, 96228, 54912, 1430, 0, 1, 9, 128, 1715, 18144, 131250, 540672, 938223, 366080, 4862, 0
Offset: 0

Views

Author

Ilya Gutkovskiy, Aug 07 2017

Keywords

Comments

Number of 2n-length strings of balanced parentheses of at most k different types. Also number of binary trees with n inner nodes of at most k different dimensions. - Alois P. Heinz, Oct 28 2019

Examples

			G.f. of column k: A(x) = 1 + k*x + 2*k^2*x^2 + 5*k^3*x^3 + 14*k^4*x^4 + 42*k^5*x^5 + 132*k^6*x^6 + ...
Square array begins:
  1,   1,     1,      1,      1,       1,  ...
  0,   1,     2,      3,      4,       5,  ...
  0,   2,     8,     18,     32,      50,  ...
  0,   5,    40,    135,    320,     625,  ...
  0,  14,   224,   1134,   3584,    8750,  ...
  0,  42,  1344,  10206,  43008,  131250,  ...
		

Crossrefs

Rows n=0-2 give: A000012, A001477, A001105.
Main diagonal gives A291699.

Programs

  • Maple
    ctln:= proc(n) option remember; binomial(2*n, n)/(n+1) end:
    A:= proc(n, k) option remember; k^n*ctln(n) end:
    seq(seq(A(n, d-n), n=0..d), d=0..10);  # Alois P. Heinz, Oct 28 2019
  • Mathematica
    Table[Function[k, SeriesCoefficient[2/(1 + Sqrt[1 - 4 k x]), {x, 0, n}]][j - n], {j, 0, 10}, {n, 0, j}] // Flatten
    Table[Function[k, SeriesCoefficient[1/(1 + ContinuedFractionK[-k x, 1, {i, 1, n}]), {x, 0, n}]][j - n], {j, 0, 10}, {n, 0, j}] // Flatten

Formula

A(n,k) = k^n*(2*n)!/(n!*(n + 1)!).
A(n,k) = k^n*A000108(n).
G.f. of column k: 2/(1 + sqrt(1 - 4*k*x)).
G.f. of column k: 1/(1 - k*x/(1 - k*x/(1 - k*x/(1 - k*x/(1 - k*x/(1 - ...)))))), a continued fraction.
E.g.f. of column k: (BesselI(0,2*k*x) - BesselI(1,2*k*x))*exp(2*k*x).
If g.f. = 2/(1 + sqrt(1 - 4*k*x)), then a(n) ~ k^n*4^n/(sqrt(Pi)*n^(3/2)).
A(n,k) = Sum_{i=0..k} binomial(k,i) * A256061(n,k-i). - Alois P. Heinz, Oct 28 2019
For fixed k >= 1, Sum_{n>=0} 1/A(n,k) = 2*k*(8*k + 1) / (4*k - 1)^2 + 24 * k^2 * arcsin(1/(2*sqrt(k))) / (4*k - 1)^(5/2). - Vaclav Kotesovec, Nov 23 2021
For fixed k >= 1, Sum_{n>=0} (-1)^n / A(n,k) = 2*k*(8*k - 1) / (4*k + 1)^2 - 24 * k^2 * log((1 + sqrt(4*k + 1))/(2*sqrt(k))) / (4*k + 1)^(5/2). - Vaclav Kotesovec, Nov 24 2021

A156128 a(n) = 6^n * Catalan(n).

Original entry on oeis.org

1, 6, 72, 1080, 18144, 326592, 6158592, 120092544, 2401850880, 48997757952, 1015589892096, 21327387734016, 452796847276032, 9702789584486400, 209580255024906240, 4558370546791710720, 99747873141559787520, 2194453209114315325440, 48508965675158549299200
Offset: 0

Views

Author

Philippe Deléham, Feb 04 2009

Keywords

Comments

Number of Dyck n-paths with two types of up step and three types of down step. - David Scambler, Jun 21 2013

Crossrefs

Programs

  • Magma
    [6^n*Catalan(n): n in [0..20]]; // Vincenzo Librandi, Jul 19 2011
  • Maple
    A156128_list := proc(n) local j, a, w; a := array(0..n); a[0] := 1;
    for w from 1 to n do a[w] := 6*(a[w-1]+add(a[j]*a[w-j-1],j=1..w-1)) od;convert(a,list)end: A156128_list(16); # Peter Luschny, May 19 2011
  • Mathematica
    Table[CatalanNumber[n]6^n, {n, 0, 16}] (* Alonso del Arte, Jul 19 2011 *)

Formula

a(n) = 6^n * A000108(n).
From Gary W. Adamson, Jul 18 2011: (Start)
a(n) is the upper left term in M^n, M = an infinite square production matrix:
6, 6, 0, 0, 0, 0, ...
6, 6, 6, 0, 0, 0, ...
6, 6, 6, 6, 0, 0, ...
6, 6, 6, 6, 6, 0, ...
... (End)
E.g.f.: KummerM(1/2, 2, 24*x). - Peter Luschny, Aug 26 2012
G.f.: c(6*x) with c(x) the o.g.f. of A000108 (Catalan). - Philippe Deléham, Nov 15 2013
a(n) = Sum{k=0..n} A085880(n,k) * 5^k. - Philippe Deléham, Nov 15 2013
G.f.: 1/(1 - 6*x/(1 - 6*x/(1 - 6*x/(1 - ...)))), a continued fraction. - Ilya Gutkovskiy, Aug 08 2017
Sum_{n>=0} 1/a(n) = 588/529 + 864*arctan(1/sqrt(23)) / (529*sqrt(23)). - Vaclav Kotesovec, Nov 23 2021
Sum_{n>=0} (-1)^n/a(n) = 564/625 - 432*log(3/2) / 3125. - Amiram Eldar, Jan 25 2022
D-finite with recurrence (n+1)*a(n) +12*(-2*n+1)*a(n-1)=0. - R. J. Mathar, Mar 21 2022

A156266 a(n) = 7^n*Catalan(n).

Original entry on oeis.org

1, 7, 98, 1715, 33614, 705894, 15529668, 353299947, 8243665430, 196199237234, 4744454282204, 116239129913998, 2879153833254412, 71978845831360300, 1813866914950279560, 46026872966863343835, 1175038992212864189670
Offset: 0

Views

Author

Philippe Deléham, Feb 07 2009

Keywords

Crossrefs

Programs

  • Magma
    [7^n*Catalan(n): n in [0..20]]; // Vincenzo Librandi, Jul 19 2011
  • Maple
    A156266_list := proc(n) local j, a, w; a := array(0..n); a[0] := 1;
    for w from 1 to n do a[w] := 7*(a[w-1]+add(a[j]*a[w-j-1],j=1..w-1)) od;convert(a,list)end: A156266_list(16); # Peter Luschny, May 19 2011
  • Mathematica
    Table[7^n * CatalanNumber[n], {n, 0, 16}] (* Amiram Eldar, Jan 25 2022 *)

Formula

a(n) = 7^n*A000108(n).
From Gary W. Adamson, Jul 18 2011: (Start)
a(n) is the upper left term in M^n, M = an infinite square production matrix:
7, 7, 0, 0, 0, 0, ...
7, 7, 7, 0, 0, 0, ...
7, 7, 7, 7, 0, 0, ...
7, 7, 7, 7, 7, 0, ...
... (End)
E.g.f.: KummerM(1/2, 2, 28*x). - Peter Luschny, Aug 26 2012
G.f.: c(7*x) with c(x) the o.g.f. of A000108 (Catalan). - Philippe Deléham, Nov 15 2013
a(n) = Sum_{k=0..n} A085880(n,k)*6^k. - Philippe Deléham, Nov 15 2013
G.f.: 1/(1 - 7*x/(1 - 7*x/(1 - 7*x/(1 - ...)))), a continued fraction. - Ilya Gutkovskiy, Aug 08 2017
Sum_{n>=0} 1/a(n) = 266/243 + 392*arctan(1/(3*sqrt(3))) / (729*sqrt(3)). - Vaclav Kotesovec, Nov 23 2021
Sum_{n>=0} (-1)^n/a(n) = 770/841 - 1176*arctanh(1/sqrt(29)) / (841*sqrt(29)). - Amiram Eldar, Jan 25 2022
D-finite with recurrence (n+1)*a(n) +14*(-2*n+1)*a(n-1)=0. - R. J. Mathar, Mar 21 2022

Extensions

a(15) corrected by Vincenzo Librandi, Jul 19 2011

A151254 Number of walks within N^3 (the first octant of Z^3) starting at (0,0,0) and consisting of n steps taken from {(-1, 0, 0), (1, 0, 0), (1, 0, 1), (1, 1, 0), (1, 1, 1)}.

Original entry on oeis.org

1, 4, 20, 96, 480, 2368, 11840, 58880, 294400, 1468416, 7342080, 36667392, 183336960, 916144128, 4580720640, 22896574464, 114482872320, 572320645120, 2861603225600, 14306741583872, 71533707919360, 357650927714304, 1788254638571520, 8941026626502656, 44705133132513280, 223522175800311808
Offset: 0

Views

Author

Manuel Kauers, Nov 18 2008

Keywords

Comments

Hankel transform is 4^binomial(n+1,2). - Philippe Deléham, Feb 01 2009

Crossrefs

Programs

  • Magma
    [n le 3 select Factorial(n+2)/6 else (5*n*Self(n-1) + 16*(n-3)*Self(n-2) - 80*(n-3)*Self(n-3))/n: n in [1..30]]; // G. C. Greubel, Nov 09 2022
    
  • Mathematica
    aux[i_, j_, k_, n_]:= Which[Min[i, j, k, n]<0 || Max[i, j, k]>n, 0, n==0, KroneckerDelta[i, j, k, n], True, aux[i, j, k, n] = aux[-1+i, -1+j, -1+k, -1+n] + aux[-1+i, -1+j, k, -1+n] + aux[-1+i, j, -1+k, -1+n] + aux[-1+i, j, k, -1 + n] + aux[1+i, j, k, -1+n]]; Table[Sum[aux[i,j,k,n], {i,0,n}, {j,0,n}, {k,0,n}], {n, 0, 30}]
    a[n_]:= a[n]= If[n<3, (n+3)!/3!, (5*(n+1)*a[n-1] +16*(n-2)*a[n-2] -80*(n-2)*a[n- 3])/(n+1)]; Table[a[n], {n, 0, 30}] (* G. C. Greubel, Nov 09 2022 *)
  • SageMath
    def a(n): # a = A151254
        if (n==0): return 1
        elif (n%2==1): return 5*a(n-1) - 4^((n-1)/2)*catalan_number((n-1)/2)
        else: return 5*a(n-1)
    [a(n) for n in (0..30)] # G. C. Greubel, Nov 09 2022

Formula

a(n) = Sum_{k=0..n} A120730(n,k)*4^k. - Philippe Deléham, Feb 01 2009
From Philippe Deléham, Feb 02 2009: (Start)
a(2n+2) = 5*a(2n+1), a(2n+1) = 5*a(2n) - 4^n*A000108(n) = 5*a(2n) - A151403(n).
G.f.: (sqrt(1-16*x^2) + 8*x - 1)/(8*x*(1-5*x)). (End)
a(n) = (5*(n+1)*a(n-1) + 16*(n-2)*a(n-2) - 80*(n-2)*a(n-3))/(n+1). - G. C. Greubel, Nov 09 2022

A156195 a(2n+2) = 6*a(2n+1), a(2n+1) = 6*a(2n) - 5^n*A000108(n), a(0)=1.

Original entry on oeis.org

1, 5, 30, 175, 1050, 6250, 37500, 224375, 1346250, 8068750, 48412500, 290343750, 1742062500, 10450312500, 62701875000, 376177734375, 2257066406250, 13541839843750, 81251039062500, 487496738281250, 2924980429687500, 17549718554687500, 105298311328125000
Offset: 0

Views

Author

Philippe Deléham, Feb 05 2009

Keywords

Comments

Hankel transform is 5^C(n+1,2). - Philippe Deléham, Feb 05 2009

Crossrefs

Programs

  • Magma
    [n le 3 select Factorial(n+3)/24 else (6*n*Self(n-1) + 20*(n-3)*Self(n-2) - 120*(n-3)*Self(n-3))/n: n in [1..30]]; // G. C. Greubel, Nov 09 2022
    
  • Maple
    A156195 := proc(n)
        option remember;
        local nh;
        if n= 0 then
            1;
        elif  type(n,'even') then
            6*procname(n-1);
        else
            nh := floor(n/2) ;
            6*procname(n-1)-5^nh*A000108(nh) ;
        end if;
    end proc: # R. J. Mathar, Jul 21 2016
  • Mathematica
    CoefficientList[Series[(Sqrt[1-20x^2]+10x-1)/(10x(1-6x)),{x,0,30}],x] (* Harvey P. Dale, Oct 21 2016 *)
  • SageMath
    def a(n): # a = A156195
        if (n==0): return 1
        elif (n%2==1): return 6*a(n-1) - 5^((n-1)/2)*catalan_number((n-1)/2)
        else: return 6*a(n-1)
    [a(n) for n in (0..30)] # G. C. Greubel, Nov 09 2022

Formula

a(n) = Sum_{k=0..n} A120730(n,k)*5^k.
G.f.: (sqrt(1-20*x^2) +10*x -1)/(10*x*(1-6*x)). - Philippe Deléham, Feb 05 2009
(n+1)*a(n) = 6*(n+1)*a(n-1) + 20*(n-2)*a(n-2) - 120*(n-2)*a(n-3). - R. J. Mathar, Jul 21 2016

Extensions

Corrected and extended by Harvey P. Dale, Oct 21 2016

A156270 a(n) = 8^n*Catalan(n).

Original entry on oeis.org

1, 8, 128, 2560, 57344, 1376256, 34603008, 899678208, 23991418880, 652566593536, 18034567675904, 504967894925312, 14294475794808832, 408413594137395200, 11762311511156981760, 341107033823552471040, 9952299339793060331520
Offset: 0

Views

Author

Philippe Deléham, Feb 07 2009

Keywords

Comments

A quarter of the count of And/Or-Trees with 2 variables [Chauvin]. - R. J. Mathar, Apr 01 2012

Crossrefs

Programs

Formula

a(n) = 8^n*A000108(n).
From Gary W. Adamson, Jul 18 2011: (Start)
a(n) is the upper left term in M^n, M = an infinite square production matrix:
8, 8, 0, 0, 0, 0, ...
8, 8, 8, 0, 0, 0, ...
8, 8, 8, 8, 0, 0, ...
8, 8, 8, 8, 8, 0, ...
... (End)
E.g.f.: KummerM(1/2, 2, 32*x). - Peter Luschny, Aug 26 2012
G.f.: c(8*x) with c(x) the o.g.f. of A000108 (Catalan). - Philippe Deléham, Nov 15 2013
a(n) = Sum_{k=0..n} A085880(n,k)*7^k. - Philippe Deléham, Nov 15 2013
G.f.: 1/(1 - 8*x/(1 - 8*x/(1 - 8*x/(1 - ...)))), a continued fraction. - Ilya Gutkovskiy, Aug 08 2017
(n+1)*a(n) +16*(-2*n+1)*a(n-1)=0. - R. J. Mathar, Apr 14 2018
Sum_{n>=0} 1/a(n) = 1040/961 + 1536*arctan(1/sqrt(31)) / (961*sqrt(31)). - Vaclav Kotesovec, Nov 23 2021
Sum_{n>=0} (-1)^n/a(n) = 112/121 - 512*arctanh(1/sqrt(33)) / (363*sqrt(33)). - Amiram Eldar, Jan 25 2022
D-finite with recurrence +(n+1)*a(n) +16*(-2*n+1)*a(n-1)=0. - R. J. Mathar, Mar 21 2022

A156273 a(n) = 9^n*Catalan(n).

Original entry on oeis.org

1, 9, 162, 3645, 91854, 2480058, 70150212, 2051893701, 61556811030, 1883638417518, 58564030799196, 1844766970174674, 58748732742485772, 1888352123865614100, 61182608813245896840, 1996082612532147384405, 65518476340761072970470, 2162109719245115408025510
Offset: 0

Views

Author

Philippe Deléham, Feb 07 2009

Keywords

Crossrefs

Programs

  • Magma
    [9^n*Catalan(n): n in [0..20]]; // Vincenzo Librandi, Jul 19 2011
  • Mathematica
    Table[9^n CatalanNumber[n],{n,0,20}] (* Harvey P. Dale, Sep 09 2012 *)

Formula

a(n) = 9^n*A000108(n).
From Gary W. Adamson, Jul 18 2011: (Start)
a(n) is the upper left term in M^n, M = an infinite square production matrix:
9, 9, 0, 0, 0, 0, ...
9, 9, 9, 0, 0, 0, ...
9, 9, 9, 9, 0, 0, ...
9, 9, 9, 9, 9, 0, ...
... (End)
E.g.f.: KummerM(1/2, 2, 36*x). - Peter Luschny, Aug 26 2012
G.f.: c(9*x) with c(x) the o.g.f. of A000108 (Catalan). - Philippe Deléham, Nov 15 2013
a(n) = Sum{k=0..n} A085880(n,k)*8^k. - Philippe Deléham, Nov 15 2013
G.f.: 1/(1 - 9*x/(1 - 9*x/(1 - 9*x/(1 - ...)))), a continued fraction. - Ilya Gutkovskiy, Aug 08 2017
Sum_{n>=0} 1/a(n) = 1314/1225 + 1944*arctan(1/sqrt(35)) / (1225*sqrt(35)). - Vaclav Kotesovec, Nov 23 2021
Sum_{n>=0} (-1)^n/a(n) = 1278/1369 - 1944*arctanh(1/sqrt(37)) / (1369*sqrt(37)). - Amiram Eldar, Jan 25 2022
D-finite with recurrence (n+1)*a(n) +18*(-2*n+1)*a(n-1)=0. - R. J. Mathar, Mar 21 2022

A156275 a(n) = 10^n*Catalan(n).

Original entry on oeis.org

1, 10, 200, 5000, 140000, 4200000, 132000000, 4290000000, 143000000000, 4862000000000, 167960000000000, 5878600000000000, 208012000000000000, 7429000000000000000, 267444000000000000000, 9694845000000000000000, 353576700000000000000000
Offset: 0

Views

Author

Philippe Deléham, Feb 07 2009

Keywords

Comments

In general, for m >= 1, Sum_{k>=0} 1/(m^k * Catalan(k)) = 2*m*(8*m + 1) / (4*m - 1)^2 + 24 * m^2 * arcsin(1/(2*sqrt(m))) / (4*m - 1)^(5/2). - Vaclav Kotesovec, Nov 23 2021

Crossrefs

Programs

  • Magma
    [10^n*Catalan(n): n in [0..20]]; // Vincenzo Librandi, Jul 19 2011
  • Mathematica
    Table[10^n CatalanNumber[n],{n,0,20}] (* Harvey P. Dale, Mar 12 2013 *)

Formula

a(n) = 10^n*A000108(n).
From Gary W. Adamson, Jul 18 2011: (Start)
a(n) is the upper left term in M^n, M = an infinite square production matrix:
10, 10, 0, 0, 0, ...
10, 10, 10, 0, 0, ...
10, 10, 10, 10, 0, ...
10, 10, 10, 10, 10, ...
... (End)
E.g.f.: KummerM(1/2, 2, 40*x). - Peter Luschny, Aug 26 2012
G.f.: c(10*x) with c(x) the o.g.f. of A000108 (Catalan). - Philippe Deléham, Nov 15 2013
a(n) = Sum_{k=0..n} A085880(n,k)*9^k. - Philippe Deléham, Nov 15 2013
G.f.: 1/(1 - 10*x/(1 - 10*x/(1 - 10*x/(1 - ...)))), a continued fraction. - Ilya Gutkovskiy, Aug 08 2017
Sum_{n>=0} 1/a(n) = 180/169 + 800*arctan(1/sqrt(39)) / (507*sqrt(39)). - Vaclav Kotesovec, Nov 23 2021
Sum_{n>=0} (-1)^n/a(n) = 1580/1681 - 2400*arctanh(1/sqrt(41)) / (1681*sqrt(41)). - Amiram Eldar, Jan 25 2022
D-finite with recurrence (n+1)*a(n) +20*(-2*n+1)*a(n-1)=0. - R. J. Mathar, Mar 21 2022

Extensions

a(15) corrected by Vincenzo Librandi, Jul 19 2011

A354736 a(0) = a(1) = 1; a(n) = 5 * Sum_{k=0..n-2} a(k) * a(n-k-2).

Original entry on oeis.org

1, 1, 5, 10, 55, 150, 775, 2550, 12500, 46250, 219375, 875000, 4075000, 17071250, 78796875, 341100000, 1569350000, 6947531250, 31966000000, 143761750000, 662668906250, 3014440000000, 13932834296875, 63921914062500, 296358191406250, 1368603488281250, 6365085546875000
Offset: 0

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Author

Ilya Gutkovskiy, Jun 04 2022

Keywords

Crossrefs

Programs

  • Mathematica
    a[0] = a[1] = 1; a[n_] := a[n] = 5 Sum[a[k] a[n - k - 2], {k, 0, n - 2}]; Table[a[n], {n, 0, 26}]
    nmax = 26; CoefficientList[Series[(1 - Sqrt[1 - 20 x^2 (1 + x)])/(10 x^2), {x, 0, nmax}], x]

Formula

G.f. A(x) satisfies: A(x) = 1 + x + 5 * (x * A(x))^2.
G.f.: (1 - sqrt(1 - 20 * x^2 * (1 + x))) / (10 * x^2).
a(n) ~ sqrt((2+3*r)*(1+r)) / (sqrt(Pi) * n^(3/2) * r^n), where r = 2*cos(arccos(-13/40)/3)/3 - 1/3. - Vaclav Kotesovec, Jun 04 2022
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