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 1-4 of 4 results.

A013698 a(n) = binomial(3*n+2, n-1).

Original entry on oeis.org

1, 8, 55, 364, 2380, 15504, 100947, 657800, 4292145, 28048800, 183579396, 1203322288, 7898654920, 51915526432, 341643774795, 2250829575120, 14844575908435, 97997533741800, 647520696018735, 4282083008118300
Offset: 1

Views

Author

Joachim.Rosenthal(AT)nd.edu (Joachim Rosenthal), Emeric Deutsch

Keywords

Comments

Degree of variety K_{2,n}^1. Also number of double-rises (or odd-level peaks) in all generalized {(1,2),(1,-1)}-Dyck paths of length 3(n+1).
Number of dissections of a convex (2n+2)-gon by n-2 noncrossing diagonals into (2j+2)-gons, 1<=j<=n-1.
a(n) is the number of lattice paths from (0,0) to (3n+1,n-1) avoiding two consecutive up-steps. - Shanzhen Gao, Apr 20 2010

Crossrefs

Cf. A013699 (q=2), A013700 (q=3), A013701 (q=4), A013702 (q=5).

Programs

Formula

G.f.: g/((g-1)^3*(3*g-1)) where g*(1-g)^2 = x. - Mark van Hoeij, Nov 09 2011
a(n) = Sum_{k=0..n-1} binomial(2*n+k+2,k). - Arkadiusz Wesolowski, Apr 02 2012
D-finite with recurrence 2*(2*n+3)*(n+1)*a(n) -n*(67*n+34)*a(n-1) +30*(3*n-1)*(3*n-2)*a(n-2)=0. - R. J. Mathar, Feb 05 2013
a(n+1) = (3*n+5)*(3*n+4)*(3*n+3)*a(n)/((2*n+5)*(2*n+4)*n). - Robert Israel, Aug 09 2015
With offset 0, the o.g.f. equals f(x)*g(x)^5, where f(x) is the o.g.f. for A005809 and g(x) is the o.g.f. for A001764. More generally, f(x)*g(x)^k is the o.g.f. for the sequence binomial(3*n + k,n). Cf. A045721 (k = 1), A025174 (k = 2), A004319 (k = 3), A236194 (k = 4), A165817 (k = -1), A117671 (k = -2). - Peter Bala, Nov 04 2015

A013702 Degree of variety K_{2,n}^5.

Original entry on oeis.org

1, 2048, 832040, 193710244, 34673583028, 5372862566400, 763562937059280, 102703589621825280, 13319075453502743045, 1684658996331320739600, 209381188023138094045641, 25698882980999585848747760
Offset: 1

Views

Author

Joachim.Rosenthal(AT)nd.edu (Joachim Rosenthal)

Keywords

Crossrefs

Cf. A013698 (q=1), A013699 (q=2), A013700 (q=3), A013701 (q=4).

Programs

  • PARI
    K(n,q=5)=(2*n+n*q+2*q)!*sum(j=0,q,((q-2*j)*(n+2)+1)/(n+j*(n+2))!/(n+1+(q-j)*(n+2))!)

Extensions

Edited by Ralf Stephan, May 13 2003

A013699 Degree of variety K_{2,n}^2.

Original entry on oeis.org

1, 32, 610, 9842, 147798, 2145600, 30664890, 435668420, 6186432967, 88066807556, 1258885297696, 18084694597452, 261164661944060, 3791317346771584, 55316720239735242, 810944384733610356
Offset: 1

Views

Author

Joachim.Rosenthal(AT)nd.edu (Joachim Rosenthal)

Keywords

Comments

Number of Catalan paths (nonnegative, starting and ending at 0, step +/-1) of 4n+4 steps with all values less than or equal to n+1 (see A080934).

Crossrefs

Cf. A013698 (q=1), A013700 (q=3), A013701 (q=4), A013702 (q=5).

Programs

  • PARI
    K(n,q=2)=(2*n+n*q+2*q)!*sum(j=0,q,((q-2*j)*(n+2)+1)/(n+j*(n+2))!/(n+1+(q-j)*(n+2))!)

A013700 Degree of variety K_{2,n}^3.

Original entry on oeis.org

1, 128, 6765, 265720, 9112264, 290926848, 8916942687, 266668876540, 7853149169635, 228982270335000, 6632994268595136, 191292945772217856, 5500214758962096400, 157819424038439232000, 4521902974531722618723
Offset: 1

Views

Author

Joachim.Rosenthal(AT)nd.edu (Joachim Rosenthal)

Keywords

Crossrefs

Cf. A013698 (q=1), A013699 (q=2), A013701 (q=4), A013702 (q=5).

Programs

  • PARI
    K(n,q=3)=(2*n+n*q+2*q)!*sum(j=0,q,((q-2*j)*(n+2)+1)/(n+j*(n+2))!/(n+1+(q-j)*(n+2))!)

Extensions

Edited by Ralf Stephan, May 13 2003
Showing 1-4 of 4 results.