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.

Previous Showing 21-27 of 27 results.

A176992 Triangle T(n,m) = binomial(2n-k+1, n+1) read by rows, 0 <= k <= n.

Original entry on oeis.org

1, 3, 1, 10, 4, 1, 35, 15, 5, 1, 126, 56, 21, 6, 1, 462, 210, 84, 28, 7, 1, 1716, 792, 330, 120, 36, 8, 1, 6435, 3003, 1287, 495, 165, 45, 9, 1, 24310, 11440, 5005, 2002, 715, 220, 55, 10, 1, 92378, 43758, 19448, 8008, 3003, 1001, 286, 66, 11, 1, 352716, 167960, 75582, 31824, 12376, 4368, 1365, 364, 78, 12, 1
Offset: 0

Views

Author

Roger L. Bagula, Dec 08 2010

Keywords

Comments

Row sums are A001791.
Obtained from A059481 by removal of the last two terms in each row, followed by row reversal.
Riordan array (c(x)/sqrt(1 - 4*x), x*c(x)) where c(x) is the g.f. of A000108. - Philippe Deléham, Jul 12 2015

Examples

			Triangle begins:
       1;
       3,      1;
      10,      4,     1;
      35,     15,     5,     1;
     126,     56,    21,     6,    1;
     462,    210,    84,    28,    7,     1;
    1716,    792,   330,   120,   36,     8,    1;
    6435,   3003,  1287,   495,   165,   45,    9,   1;
   24310,  11440,  5005,  2002,   715,  220,   55,  10,  1;
   92378,  43758, 19448,  8008,  3003, 1001,  286,  66, 11,  1;
  352716, 167960, 75582, 31824, 12376, 4368, 1365, 364, 78, 12, 1;
		

Crossrefs

Cf. Similar triangle: A033184, A054445.
Cf. A178300 (reversal).

Programs

  • Magma
    /* As triangle */ [[Binomial(2*n-k+1,n+1): k in [0..n]]: n in [0.. 10]]; // Vincenzo Librandi, Jul 12 2015
  • Maple
    A176992 := proc(n,k) binomial(1+2*n-k,n+1) ; end proc: # R. J. Mathar, Dec 09 2010
  • Mathematica
    p[t_, j_] = ((-1)^(j + 1)/2)*Sum[Binomial[k - j - 1, j + 1]*t^k, {k, 0, Infinity}];
    Flatten[Table[CoefficientList[ExpandAll[p[t, j]], t], {j, 0, 10}]]

Formula

n-th row of the triangle = top row of M^n, where M is the following infinite square production matrix:
3, 1, 0, 0, 0, ...
1, 1, 1, 0, 0, ...
1, 1, 1, 1, 0, ...
1, 1, 1, 1, 1, ...
... - Philippe Deléham, Jul 12 2015

A213808 Triangle of numbers C^(7)(n,k) of combinations with repetitions from n different elements over k for each of them not more than 7 appearances allowed.

Original entry on oeis.org

1, 1, 1, 1, 2, 3, 1, 3, 6, 10, 1, 4, 10, 20, 35, 1, 5, 15, 35, 70, 126, 1, 6, 21, 56, 126, 252, 462, 1, 7, 28, 84, 210, 462, 924, 1716, 1, 8, 36, 120, 330, 792, 1716, 3432, 6427, 1, 9, 45, 165, 495, 1287, 3003, 6435, 12861, 24229, 1, 10, 55, 220, 715, 2002, 5005, 11440, 24300, 48520, 91828
Offset: 0

Views

Author

Keywords

Comments

For k <= 6, the triangle coincides with triangle A213745.

Examples

			Triangle begins
n/k |  0     1     2     3     4     5     6     7     8
----+---------------------------------------------------
  0 |  1
  1 |  1     1
  2 |  1     2     3
  3 |  1     3     6    10
  4 |  1     4    10    20    35
  5 |  1     5    15    35    70   126
  6 |  1     6    21    56   126   252   462
  7 |  1     7    28    84   210   462   924  1716
  8 |  1     8    36   120   330   792  1716  3432  6427
		

Crossrefs

Programs

  • Mathematica
    Table[Sum[(-1)^r*Binomial[n, r]*Binomial[n - 8*r + k - 1, n - 1], {r, 0, Floor[k/8]}], {n, 0, 10}, {k, 0, n}] // Flatten (* G. C. Greubel, Nov 25 2017 *)
  • PARI
    for(n=0,10, for(k=0,n, print1(if(n==0 && k==0, 1, sum(r=0, floor(k/8), (-1)^r*binomial(n,r)*binomial(n-8*r + k-1,n-1))), ", "))) \\ G. C. Greubel, Nov 25 2017

Formula

T(n,k) = Sum_{r=0..floor(k/8)} (-1)^r*C(n,r)*C(n-8*r+k-1, n-1).
T(n,0)=1, T(n,1)=n, T(n,2)=A000217(n) for n > 1, T(n,3)=A000292(n) for n >= 3, T(n,4)=A000332(n) for n >= 7, T(n,5)=A000389(n) for n >= 9, T(n,6)=A000579(n) for n >= 11, T(n,7)=A000580(n) for n >= 13.

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[%]

A174952 Triangle t(n,m)= binomial(n+m-1,n-1) + binomial(2*n-m-1,n-1) -binomial(2*n-1,n-1) read by rows, 0<=m<=n.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, -1, -1, 1, 1, -11, -15, -11, 1, 1, -51, -76, -76, -51, 1, 1, -204, -315, -350, -315, -204, 1, 1, -785, -1226, -1422, -1422, -1226, -785, 1, 1, -2995, -4683, -5523, -5775, -5523, -4683, -2995, 1, 1, -11431, -17830, -21142, -22528, -22528
Offset: 0

Views

Author

Roger L. Bagula, Apr 02 2010

Keywords

Comments

Row sums are 1, 2, 3, 0, -35, -252, -1386, -6864, -32175, -145860, -646646,....

Examples

			1;
1, 1;
1, 1, 1;
1, -1, -1, 1;
1, -11, -15, -11, 1;
1, -51, -76, -76, -51, 1;
1 -204, -315, -350, -315, -204, 1;
1, -785, -1226, -1422, -1422, -1226, -785, 1;
1, -2995, -4683, -5523, -5775, -5523, -4683, -2995, 1;
1, -11431, -17830, -21142, -22528, -22528, -21142, -17830, -11431, 1;
1, -43748, -68013, -80718, -86658, -88374, -86658, -80718, -68013, -43748, 1;
		

Crossrefs

Programs

  • Maple
    A174952 := proc(n,m)
            binomial(n+m-1,n-1)+binomial(2*n-m-1,n-1) -binomial(2*n-1,n-1);
    end proc: # R. J. Mathar, Jan 15 2013

Formula

t(n,m) = t(n,n-m).

Extensions

Definition corrected and deobfuscated. R. J. Mathar, Jan 15 2013

A343936 Number of ways to choose a multiset of n divisors of n - 1.

Original entry on oeis.org

1, 2, 3, 10, 5, 56, 7, 120, 45, 220, 11, 4368, 13, 560, 680, 3876, 17, 26334, 19, 42504, 1771, 2024, 23, 2035800, 325, 3276, 3654, 201376, 29, 8347680, 31, 376992, 6545, 7140, 7770, 145008513, 37, 9880, 10660, 53524680, 41, 73629072, 43, 1712304, 1906884
Offset: 1

Views

Author

Gus Wiseman, May 05 2021

Keywords

Examples

			The a(1) = 1 through a(5) = 5 multisets:
  {}  {1}  {1,1}  {1,1,1}  {1,1,1,1}
      {2}  {1,3}  {1,1,2}  {1,1,1,5}
           {3,3}  {1,1,4}  {1,1,5,5}
                  {1,2,2}  {1,5,5,5}
                  {1,2,4}  {5,5,5,5}
                  {1,4,4}
                  {2,2,2}
                  {2,2,4}
                  {2,4,4}
                  {4,4,4}
The a(6) = 56 multisets:
  11111  11136  11333  12236  13366  22266  23666
  11112  11166  11336  12266  13666  22333  26666
  11113  11222  11366  12333  16666  22336  33333
  11116  11223  11666  12336  22222  22366  33336
  11122  11226  12222  12366  22223  22666  33366
  11123  11233  12223  12666  22226  23333  33666
  11126  11236  12226  13333  22233  23336  36666
  11133  11266  12233  13336  22236  23366  66666
		

Crossrefs

The version for chains of divisors is A163767.
Diagonal n = k + 1 of A343658.
Choosing n divisors of n gives A343935.
A000005 counts divisors.
A000312 = n^n.
A007318 counts k-sets of elements of {1..n}.
A009998 = n^k (as an array, offset 1).
A059481 counts k-multisets of elements of {1..n}.
A146291 counts divisors of n with k prime factors (with multiplicity).
A253249 counts nonempty chains of divisors of n.
Strict chains of divisors:
- A067824 counts strict chains of divisors starting with n.
- A074206 counts strict chains of divisors from n to 1.
- A251683 counts strict length k + 1 chains of divisors from n to 1.
- A334996 counts strict length-k chains of divisors from n to 1.
- A337255 counts strict length-k chains of divisors starting with n.
- A337256 counts strict chains of divisors of n.
- A343662 counts strict length-k chains of divisors.

Programs

  • Mathematica
    multchoo[n_,k_]:=Binomial[n+k-1,k];
    Table[multchoo[DivisorSigma[0,n],n-1],{n,50}]

Formula

a(n) = ((sigma(n - 1), n)) = binomial(sigma(n - 1) + n - 1, n) where sigma = A000005 and binomial = A007318.

A241188 Triangle T(n,s) of Dynkin type D_n read by rows (n >= 2, 0 <= s <= n).

Original entry on oeis.org

1, 2, 1, 1, 3, 5, 5, 1, 4, 9, 16, 20, 1, 5, 14, 30, 55, 77, 1, 6, 20, 50, 105, 196, 294, 1, 7, 27, 77, 182, 378, 714, 1122, 1, 8, 35, 112, 294, 672, 1386, 2640, 4290, 1, 9, 44, 156, 450, 1122, 2508, 5148, 9867, 16445
Offset: 2

Views

Author

N. J. A. Sloane, Apr 24 2014

Keywords

Examples

			Triangle begins:
1, 2, 1,
1, 3, 5, 5,
1, 4, 9, 16, 20,
1, 5, 14, 30, 55, 77,
1, 6, 20, 50, 105, 196, 294,
1, 7, 27, 77, 182, 378, 714, 1122,
1, 8, 35, 112, 294, 672, 1386, 2640, 4290,
1, 9, 44, 156, 450, 1122, 2508, 5148, 9867, 16445,
...
		

Crossrefs

See A009766 for the case of type A.
See A059481 for the case of type B/C.
Diagonals give A029869, A051960, A029651, A051924. Row sums are also A051924.

Programs

  • Mathematica
    f[t_, s_] := Binomial[t, s] (s + t)/t;
    T[, 0] = 1; T[n, n_] := f[2 n - 2, n - 2]; T[n_, s_] := f[n + s - 2, s];
    Table[T[n, s], {n, 2, 9}, {s, 0, n}] // Flatten (* Jean-François Alcover, Feb 12 2019 *)

Formula

T(n,s) = [n+s-2,s] for 0 <= s < n, T(n,n) = [2n-2,n-2], where [t,s] stands for binomial(t,s)*(s+t)/t.

A316140 Denominator of the autosequence 2/((n+2)*(n+3)) difference table written by antidiagonals.

Original entry on oeis.org

3, 6, 6, 10, 15, 10, 15, 30, 30, 15, 21, 105, 70, 105, 21, 28, 84, 140, 140, 84, 28, 36, 126, 252, 315, 252, 126, 36, 45, 180, 420, 630, 630, 420, 180, 45, 55, 495, 660, 1155, 1386, 1155, 660, 495, 55, 66, 330
Offset: 0

Views

Author

Paul Curtz, Jun 25 2018

Keywords

Examples

			Difference table:
   1/3,   1/6,    1/10,   1/15,  ...
  -1/6,  -1/15,  -1/30,  -2/105, ...
   1/10,  1/30,   1/70,   1/140, ...
  -1/15, -2/105, -1/140, -1/315, ... .
  ...
Table starts:
   3   6   10    15    21    28   ...
   6  15   30   105    84   126   ...
  10  30   70   140   252   420   ...
  15 105  140   315   630  1155   ...
  21  84  252   630  1386  2772   ...
  ...
As a triangle:
   3;
   6,  6;
  10, 15, 10;
  15, 30, 30, 15;
  ...
		

Crossrefs

Cf. A000217, A003506, A033876? (main diagonal), A059481, A109613.

Programs

  • PARI
    tabl(nn) = {nn = 2*nn; m = matrix(nn, nn, n, k, if (n==1, 2/((k+1)*(k+2)))); for (n=2, nn, for (k=1, nn-n +1, m[n, k] = m[n-1, k+1] - m[n-1,k];);); nn = nn/2; matrix(nn, nn, n, k, denominator(m[n,k]));} \\ Michel Marcus, Jul 05 2018
Previous Showing 21-27 of 27 results.