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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A239103 Triangular array read by rows, arising from enumeration of binary words containing n 0's and k 1's that avoid the pattern 1011101.

Original entry on oeis.org

1, 2, 1, 6, 3, 1, 20, 10, 4, 1, 70, 35, 15, 5, 1, 248, 123, 54, 20, 6, 1, 894, 442, 198, 78, 26, 7, 1, 3264, 1611, 732, 300, 108, 33, 8, 1, 12036, 5936, 2727, 1150, 437, 146, 41, 9, 1, 44722, 22047, 10214, 4398, 1736, 617, 192, 50, 10, 1
Offset: 0

Views

Author

N. J. A. Sloane, Mar 25 2014

Keywords

Examples

			Triangle begins:
     1
     2    1
     6    3   1
    20   10   4   1
    70   35  15   5   1
   248  123  54  20   6  1
   894  442 198  78  26  7 1
  3264 1611 732 300 108 33 8 1
  ...
		

Crossrefs

See A046899 for a closely related triangle. Cf. A246971.

Programs

  • Python
    from itertools import combinations
    A239103_list = []
    for n in range(16):
        for k in range(n, -1, -1):
            c, d0 = 0, ['0']*(n+k)
            for x in combinations(range(n+k), n):
                d = list(d0)
                for i in x:
                    d[i] = '1'
                if not '1011101' in ''.join(d):
                    c += 1
            A239103_list.append(c) # Chai Wah Wu, Sep 12 2014

Extensions

More terms from Chai Wah Wu, Sep 12 2014

A328901 Triangle T(n, k) read by rows: T(n, k) is the numerator of the rational Catalan number defined as binomial(n + k, n)/(n + k) for n > 0 and T(0, 0) = 1.

Original entry on oeis.org

1, 1, 1, 1, 1, 3, 1, 1, 2, 10, 1, 1, 5, 5, 35, 1, 1, 3, 7, 14, 126, 1, 1, 7, 28, 21, 42, 77, 1, 1, 4, 12, 30, 66, 132, 1716, 1, 1, 9, 15, 165, 99, 429, 429, 6435, 1, 1, 5, 55, 55, 143, 1001, 715, 1430, 24310, 1, 1, 11, 22, 143, 1001, 1001, 1144, 2431, 4862, 46189, 1, 1, 6, 26, 91, 273, 728, 1768, 3978, 8398, 16796, 352716
Offset: 0

Views

Author

Stefano Spezia, Oct 30 2019

Keywords

Examples

			n\k|   0   1   2   3   4   5   6
---+----------------------------
0  |   1
1  |   1   1
2  |   1   1   3
3  |   1   1   2  10
4  |   1   1   5   5  35
5  |   1   1   3   7  14 126
6  |   1   1   7  28  21  42  77
...
		

Crossrefs

Main diagonal gives A201058 (for n>0).
Cf. A000108, A046899, A051162, A328902 (denominator).

Programs

  • Mathematica
    Flatten[Join[{1},Table[LCM[Binomial[n+k,n],n+k]/(n+k),{n,1,11},{k,0,n}]]]

Formula

T(n, k) = lcm(binomial(n + k, n), n + k)/(n + k) for n > 0.

A328902 Triangle T(n, k) read by rows: T(n, k) is the denominator of the rational Catalan number defined as binomial(n + k, n)/(n + k) for 0 <= k <= n, n > 0; T(0, 0) = 1.

Original entry on oeis.org

1, 1, 1, 2, 1, 2, 3, 1, 1, 3, 4, 1, 2, 1, 4, 5, 1, 1, 1, 1, 5, 6, 1, 2, 3, 1, 1, 1, 7, 1, 1, 1, 1, 1, 1, 7, 8, 1, 2, 1, 4, 1, 2, 1, 8, 9, 1, 1, 3, 1, 1, 3, 1, 1, 9, 10, 1, 2, 1, 2, 5, 2, 1, 1, 1, 5, 11, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 11, 12, 1, 2, 3, 4, 1, 3, 1, 2, 3, 1, 1, 6
Offset: 0

Views

Author

Stefano Spezia, Oct 30 2019

Keywords

Examples

			n\k| 0 1 2 3 4 5 6
---+--------------
0  | 1
1  | 1 1
2  | 2 1 2
3  | 3 1 1 3
4  | 4 1 2 1 4
5  | 5 1 1 1 1 5
6  | 6 1 2 3 1 1 1
...
		

Crossrefs

Cf. A000108, A028310 (1st column), A046899, A051162, A328901 (numerator).

Programs

  • Mathematica
    Flatten[Join[{1},Table[(n+k)/GCD[n+k,Binomial[n+k,n]],{n,1,12},{k,0,n}]]]
  • PARI
    A328902(n,k)=if(n,(n+k)/gcd(binomial(n+k,n),n+k),1) \\ M. F. Hasler, Nov 04 2019

Formula

T(n, k) = (n + k)/gcd(binomial(n + k, n), n + k) for n > 0.

A371400 Triangle read by rows: T(n, k) = binomial(k + n, k)*binomial(2*n - k, n).

Original entry on oeis.org

1, 2, 2, 6, 9, 6, 20, 40, 40, 20, 70, 175, 225, 175, 70, 252, 756, 1176, 1176, 756, 252, 924, 3234, 5880, 7056, 5880, 3234, 924, 3432, 13728, 28512, 39600, 39600, 28512, 13728, 3432, 12870, 57915, 135135, 212355, 245025, 212355, 135135, 57915, 12870
Offset: 0

Views

Author

Peter Luschny, Mar 21 2024

Keywords

Comments

The main diagonal and column 0 of the triangle are the central binomial coefficients, which are the sums of the squares of Pascal's triangle entries. This sum representation can be generalized, and all terms can be seen as sums of coefficients of some polynomials. (See the Example section.)
To see this, consider T(n, k) as the value of the polynomials P(n, k)(x) at x = 1, where P(n, k)(x) = H([-n, -k], [1], x)*H([-n, -n + k], [1], x) and H denotes the hypergeometric sum 2F1. For instance column 0 is given by the row sums of A008459, and column 1 by the row sums of A371401.

Examples

			Triangle starts:
[0]    1;
[1]    2,     2;
[2]    6,     9,     6;
[3]   20,    40,    40,    20;
[4]   70,   175,   225,   175,    70;
[5]  252,   756,  1176,  1176,   756,   252;
[6]  924,  3234,  5880,  7056,  5880,  3234,   924;
[7] 3432, 13728, 28512, 39600, 39600, 28512, 13728, 3432;
.
Because of the symmetry, only the sum representation of terms with k <= n/2 are shown.
0:                 [1]
1:               [1+1]
2:             [1+4+1],               [1+4+4]
3:           [1+9+9+1],            [1+9+21+9]
4:      [1+16+36+16+1],       [1+16+66+76+16],        [1+16+76+96+36]
5: [1+25+100+100+25+1], [1+25+160+340+205+25], [1+25+190+460+400+100]
		

Crossrefs

Column 0 and main diagonal are A000984.
Column 1 and subdiagonal are A097070.
Row sums are A045721.
The even bisection of the alternating row sums is A005809.
The central terms are A188662.

Programs

  • Maple
    T := (n, k) -> binomial(k + n, k) * binomial(2*n - k, n):
    seq(print(seq(T(n, k), k = 0..n)), n = 0..8);
  • Mathematica
    T[n_, k_] := Hypergeometric2F1[-n, -k, 1, 1] Hypergeometric2F1[-n, -n +k, 1, 1];
    Table[T[n, k], {n, 0, 7}, {k, 0, n}]

Formula

T(n, k) = A046899(n, k) * A092392(n, k).
T(n, k) = A046899(n, k) * A046899(n, n - k).
T(n, k) = A092392(n, k) * A092392(n, n - k).
T(n, k) = A371395(n, k) * (n + 1).
T(n, k) = hypergeom([-n, -k], [1], 1) * hypergeom([-n, -n + k], [1], 1).
2^n*Sum_{k=0..n} T(n, k)*(1/2)^k = A244038(n).
2^n*Sum_{k=0..n} T(n, k)*(-1/2)^k = A371399(n).

A223540 Matrix T(m,n) = nim-product(2^m,2^n) read by rows of lower triangle.

Original entry on oeis.org

1, 2, 3, 4, 8, 6, 8, 12, 11, 13, 16, 32, 64, 128, 24, 32, 48, 128, 192, 44, 52, 64, 128, 96, 176, 75, 141, 103, 128, 192, 176, 208, 141, 198, 185, 222, 256, 512, 1024, 2048, 4096, 8192, 16384, 32768, 384, 512, 768, 2048, 3072, 8192, 12288
Offset: 0

Views

Author

Tilman Piesk, Mar 21 2013

Keywords

Comments

More compact representation of the symmetric matrix A223541.
This sequence is related to A223541, as A046899 is to A007318.

Crossrefs

Cf. A223541.

A295612 a(n) = Sum_{k=0..n} binomial(n+k,k)^k.

Original entry on oeis.org

1, 3, 40, 8105, 24053106, 1016507243472, 622366942086680904, 5608321882919220905812521, 752711651805019773658037206391596, 1518219710649896586598445898967340890577318, 46343146356260529633020448755386347142785083052620084
Offset: 0

Views

Author

Ilya Gutkovskiy, Nov 24 2017

Keywords

Crossrefs

Programs

  • Mathematica
    Table[Sum[Binomial[n + k, k]^k, {k, 0, n}], {n, 0, 10}]
    Table[Sum[((n + k)!/(n! k!))^k, {k, 0, n}], {n, 0, 10}]
  • PARI
    a(n) = sum(k=0, n, binomial(n+k,k)^k); \\ Michel Marcus, Nov 25 2017

Formula

a(n) = Sum_{k=0..n} A046899(n,k)^k.
a(n) ~ 2^(2*n^2) / (exp(1/8) * Pi^(n/2) * n^(n/2)). - Vaclav Kotesovec, Nov 25 2017

A130746 Triangle read by rows: T(n,m) = binomial(n+m,1+n), 1<=m<=n.

Original entry on oeis.org

1, 1, 4, 1, 5, 15, 1, 6, 21, 56, 1, 7, 28, 84, 210, 1, 8, 36, 120, 330, 792, 1, 9, 45, 165, 495, 1287, 3003, 1, 10, 55, 220, 715, 2002, 5005, 11440, 1, 11, 66, 286, 1001, 3003, 8008, 19448, 43758, 1, 12, 78, 364, 1365, 4368, 12376, 31824, 75582, 167960
Offset: 1

Views

Author

Roger L. Bagula, Jul 12 2007

Keywords

Comments

Row sums are A002054.

Examples

			1;
1, 4;
1, 5, 15;
1, 6, 21, 56;
1, 7, 28, 84, 210;
1, 8, 36, 120, 330, 792;
1, 9, 45, 165, 495, 1287, 3003;
1, 10, 55, 220, 715, 2002, 5005, 11440;
		

Crossrefs

Programs

  • Mathematica
    Table[Table[Binomial[n + i, i + 1], {n, 1, i}], {i, 1, 10}] Flatten[%]

A171824 Triangle T(n,k)= binomial(n + k,n) + binomial(2*n-k,n) read by rows.

Original entry on oeis.org

2, 3, 3, 7, 6, 7, 21, 14, 14, 21, 71, 40, 30, 40, 71, 253, 132, 77, 77, 132, 253, 925, 469, 238, 168, 238, 469, 925, 3433, 1724, 828, 450, 450, 828, 1724, 3433, 12871, 6444, 3048, 1452, 990, 1452, 3048, 6444, 12871, 48621, 24320, 11495, 5225, 2717, 2717, 5225, 11495, 24320, 48621
Offset: 0

Views

Author

Roger L. Bagula, Dec 19 2009

Keywords

Examples

			Triangle begins as:
       2;
       3,     3;
       7,     6,     7;
      21,    14,    14,    21;
      71,    40,    30,    40,   71;
     253,   132,    77,    77,  132,  253;
     925,   469,   238,   168,  238,  469, 925;
    3433,  1724,   828,   450,  450,  828, 1724,  3433;
   12871,  6444,  3048,  1452,  990, 1452, 3048,  6444, 12871;
   48621, 24320, 11495,  5225, 2717, 2717, 5225, 11495, 24320, 48621;
  184757, 92389, 43824, 19734, 9009, 6006, 9009, 19734, 43824, 92389, 184757;
		

Crossrefs

Row sums are A000984(n+1).

Programs

  • Magma
    T:= func< n,k | Binomial(n+k,n) + Binomial(2*n-k,n) >;
    [T(n,k): k in [0..n], n in [0..12]]; // G. C. Greubel, Apr 29 2021
    
  • Mathematica
    T[n_, k_] = Binomial[n+k, k] + Binomial[2*n-k, n-k];
    Table[T[n, k], {n,0,10}, {k,0,n}]//Flatten
  • Sage
    def T(n, k): return binomial(n+k,n) + binomial(2*n-k,n)
    flatten([[T(n,k) for k in (0..n)] for n in (0..12)]) # G. C. Greubel, Apr 29 2021

Formula

T(n,k) = A046899(n,k) + A092392(n,k).
Sum_{k=0..n} T(n,k) = binomial(2*n+2, n+1) = 2*A001700(n) = A000984(n+1). - G. C. Greubel, Apr 29 2021

Extensions

Formula and row sums reference added by the Assoc. Editors of the OEIS, Feb 24 2010

A143131 Binomial transform of [1, 4, 10, 20, 0, 0, 0, ...].

Original entry on oeis.org

1, 5, 19, 63, 157, 321, 575, 939, 1433, 2077, 2891, 3895, 5109, 6553, 8247, 10211, 12465, 15029, 17923, 21167, 24781, 28785, 33199, 38043, 43337, 49101, 55355, 62119, 69413, 77257, 85671, 94675, 104289, 114533, 125427, 136991, 149245
Offset: 1

Views

Author

Gary W. Adamson, Jul 27 2008

Keywords

Examples

			a(4) = 63 = (1, 3, 3, 1) dot (1, 4, 10, 20) = (1 + 12 + 30 + 20).
		

Crossrefs

Cf. A046899.

Programs

  • Mathematica
    LinearRecurrence[{4,-6,4,-1},{1,5,19,63},37] (* or *) Rest[CoefficientList[Series[x*(1+x+5*x^2+13*x^3)/(1-x)^4,{x,0,37}],x]] (* or *) a[n_]:=(-39 + 77*n - 45*n^2 + 10*n^3)/3;Array[a,37] (* James C. McMahon, Aug 17 2025 *)

Formula

Binomial transform of [1, 4, 10, 20, 0, 0, 0, ...], where (1, 4, 10, 20) = row 3 of triangle A046899
a(n) = (-39 + 77*n - 45*n^2 + 10*n^3)/3. - T. D. Noe, Aug 22 2008
G.f.: x*(1+x+5*x^2+13*x^3)/(1-x)^4. - Colin Barker, Mar 23 2012

Extensions

More terms from T. D. Noe, Aug 22 2008

A143132 Binomial transform of [1, 5, 15, 35, 70, 0, 0, 0, ...].

Original entry on oeis.org

1, 6, 26, 96, 321, 876, 2006, 4026, 7321, 12346, 19626, 29756, 43401, 61296, 84246, 113126, 148881, 192526, 245146, 307896, 382001, 468756, 569526, 685746, 818921, 970626, 1142506, 1336276, 1553721, 1796696, 2067126, 2367006, 2698401, 3063446
Offset: 1

Views

Author

Gary W. Adamson, Jul 27 2008

Keywords

Comments

Conjecture: rightmost digit of terms is cyclic: (1, 6, 6, 6, ... repeat).

Examples

			a(4) = 96 = (1, 3, 3, 1) dot (1, 5, 15, 35) = (1 + 15 + 45 + 35).
		

Crossrefs

Cf. A046899.

Formula

Binomial transform of [1, 5, 15, 35, 70, 0, 0, 0, ...] where (1, 5, 15, 35, 70) = row 4 of triangle A046899.
From R. J. Mathar, Jul 31 2008: (Start)
O.g.f.: (1 + x + 6x^2 + 16x^3 + 46x^4)/(1-x)^5.
a(n) = 46 - 200*n + 330*A000217(n) - 245*A000292(n) + 70*A000332(n+3). (End)
a(n) = (552 - 1190*n + 895*n^2 - 280*n^3 + 35*n^4)/12. - T. D. Noe, Aug 22 2008

Extensions

More terms from T. D. Noe, Aug 22 2008
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