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 1-3 of 3 results.

A069270 Third level generalization of Catalan triangle (0th level is Pascal's triangle A007318; first level is Catalan triangle A009766; 2nd level is A069269).

Original entry on oeis.org

1, 1, 1, 1, 2, 4, 1, 3, 9, 22, 1, 4, 15, 52, 140, 1, 5, 22, 91, 340, 969, 1, 6, 30, 140, 612, 2394, 7084, 1, 7, 39, 200, 969, 4389, 17710, 53820, 1, 8, 49, 272, 1425, 7084, 32890, 135720, 420732, 1, 9, 60, 357, 1995, 10626, 53820, 254475, 1068012, 3362260
Offset: 0

Views

Author

Henry Bottomley, Mar 12 2002

Keywords

Comments

For the m-th level generalization of Catalan triangle T(n,k) = C(n+mk,k)*(n-k+1)/(n+(m-1)k+1); for n >= k+m: T(n,k) = T(n-m+1,k+1) - T(n-m,k+1); and T(n,n) = T(n+m-1,n-1) = C((m+1)n,n)/(mn+1).
Antidiagonals of convolution matrix of Table 1.5, p. 397, of Hoggatt and Bicknell. - Tom Copeland, Dec 25 2019

Examples

			Rows start
  1;
  1,   1;
  1,   2,   4;
  1,   3,   9,  22;
  1,   4,  15,  52, 140;
etc.
		

Crossrefs

Columns include A000012, A000027, A055999.
Right-hand diagonals include A002293, A069271, A006632.
Cf. A130458 (row sums).

Programs

  • Maple
    A069270 := proc(n,k)
            binomial(n+3*k,k)*(n-k+1)/(n+2*k+1) ;
    end proc: # R. J. Mathar, Oct 11 2015
  • Mathematica
    Table[Binomial[n + 3 k, k] (n - k + 1)/(n + 2 k + 1), {n, 0, 10}, {k, 0, n}] // Flatten (* Michael De Vlieger, Dec 27 2019 *)

Formula

T(n, k) = C(n+3k, k)*(n-k+1)/(n+2k+1).
For n >= k+3: T(n, k) = T(n-2, k+1)-T(n-3, k+1).
T(n, n) = T(n+2, n-1) = C(4n, n)/(3n+1).

A130457 Triangle, read by rows of 3n+1 terms, where row n+1 is generated by taking partial sums of row n and then appending 2 zeros followed by the final term in the partial sums of row n, for n>=0, with T(0,0)=1.

Original entry on oeis.org

1, 1, 0, 0, 1, 1, 1, 1, 2, 0, 0, 2, 1, 2, 3, 5, 5, 5, 7, 0, 0, 7, 1, 3, 6, 11, 16, 21, 28, 28, 28, 35, 0, 0, 35, 1, 4, 10, 21, 37, 58, 86, 114, 142, 177, 177, 177, 212, 0, 0, 212, 1, 5, 15, 36, 73, 131, 217, 331, 473, 650, 827, 1004, 1216, 1216, 1216, 1428, 0, 0, 1428, 1, 6, 21, 57
Offset: 0

Views

Author

Paul D. Hanna, May 26 2007

Keywords

Examples

			Triangle begins:
.1;
.1, 0, 0, 1;
.1, 1, 1, 2, 0, 0, 2;
.1, 2, 3, 5, 5, 5, 7, 0, 0, 7;
.1, 3, 6, 11, 16, 21, 28, 28, 28, 35, 0, 0, 35;
.1, 4, 10, 21, 37, 58, 86, 114, 142, 177, 177, 177, 212, 0, 0, 212;
.1, 5, 15, 36, 73, 131, 217, 331, 473, 650, 827, 1004, 1216, 1216, 1216, 1428, 0, 0, 1428; ...
		

Crossrefs

Cf. A130458 (final term in rows); A130456 (variant).

Programs

  • PARI
    {T(n,k)=local(A=[1],B);if(n==0,if(k==0,1,0),for(j=1,n, B=Vec(Ser(A)/(1-x));A=concat(concat(B,[0,0]),B[ #B]));A[k+1])}

A376447 a(n) = Sum_{k=1..n} binomial(n*(m+1)-m*k-1, n-k)*k/(n*m-(m-1)*k), for m=7.

Original entry on oeis.org

1, 1, 2, 11, 113, 1472, 21375, 330905, 5348380, 89188027, 1522999490, 26497322726, 468008534344, 8369663126451, 151250089239576, 2757670822707609, 50665739960395844, 937090326420476362, 17433799590092921578, 326028128575350241133, 6125291348509146395197
Offset: 0

Views

Author

Vaclav Kotesovec, Sep 23 2024, following a suggestion from Mikhail Kurkov

Keywords

Crossrefs

Cf. A000108 (m=1), A098746 (m=2), A130458 (m=3), A186182 (m=4), A186183 (m=5), A186184 (m=6).

Programs

  • Mathematica
    Join[{1}, With[{m=7}, Table[Sum[Binomial[n*(m+1)-m*k-1, n-k]*k/(n*m-(m-1)*k), {k, 1, n}], {n, 1, 20}]]]
Showing 1-3 of 3 results.