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.

A373733 Triangular numbers with tetrahedral indices: a(n) = (1/72) * (n*(n+1)*(n+2)*(n+3)*(n^2+2)).

Original entry on oeis.org

0, 1, 10, 55, 210, 630, 1596, 3570, 7260, 13695, 24310, 41041, 66430, 103740, 157080, 231540, 333336, 469965, 650370, 885115, 1186570, 1569106, 2049300, 2646150, 3381300, 4279275, 5367726, 6677685, 8243830, 10104760, 12303280
Offset: 0

Views

Author

J.S. Seneschal, Jun 17 2024

Keywords

Crossrefs

Programs

  • Mathematica
    PolygonalNumber[Binomial[Range[2, 50], 3]] (* Paolo Xausa, Jul 22 2024 *)
  • PARI
    a(n)=n*(n+1)*(n+2)*(n+3)*(n^2+2)/72 \\ Charles R Greathouse IV, Jul 10 2024
    
  • Python
    from math import comb
    def A373733(n): return comb(comb(n+2,3)+1,2) # Chai Wah Wu, Jul 10 2024

Formula

a(n) = A000217(A000292(n)).
a(n) = A000292(n) + A054563(n).

A054644 Number of labeled pure 2-complexes on n nodes with 3 2-simplexes.

Original entry on oeis.org

4, 120, 1140, 6545, 27720, 95284, 280840, 735130, 1750540, 3858140, 7971964, 15596035, 29112720, 52174360, 90223760, 151173044, 246274580, 391222160, 607525380, 924205205, 1379864024, 2025189100, 2925954200, 4166590350
Offset: 4

Views

Author

Vladeta Jovovic, Apr 15 2000

Keywords

Crossrefs

Cf. A054563.

Programs

  • Magma
    [n*(n-1)*(n-2)*(n-3)*(n^2+2)*(n^3-3*n^2+2*n-12)/1296: n in [4..30]]; // Vincenzo Librandi, Apr 30 2012
  • Mathematica
    Table[Binomial[Binomial[n,3],3],{n,4,60}] (* Vladimir Joseph Stephan Orlovsky, May 30 2010 *)
    LinearRecurrence[{10,-45,120,-210,252,-210,120,-45,10,-1},{4,120,1140,6545,27720,95284,280840,735130,1750540,3858140},30] (* Vincenzo Librandi, Apr 30 2012 *)
  • Sage
    [(binomial(binomial(n,3),3)) for n in range(4, 28)] # Zerinvary Lajos, Nov 30 2009
    

Formula

a(n) = binomial(binomial(n, 3), 3) = 4*binomial(n, 4) + 100*binomial(n, 5) + 480*binomial(n, 6) + 945*binomial(n, 7) + 840*binomial(n, 8) + 280*binomial(n, 9) = n*(n-1)*(n-2)*(n-3)*(n^2+2)*(n^3 - 3*n^2 + 2*n - 12)/1296.
G.f.: x^4*(4 + 80*x + 120*x^2 + 65*x^3 + 10*x^4 + x^5)/(1-x)^10. - Colin Barker, Jan 19 2012

Extensions

More terms from James Sellers, Apr 16 2000

A093567 Binomial (Binomial (n,2), 3) - Binomial (Binomial (n,3), 2).

Original entry on oeis.org

0, 1, 14, 75, 265, 735, 1736, 3654, 7050, 12705, 21670, 35321, 55419, 84175, 124320, 179180, 252756, 349809, 475950, 637735, 842765, 1099791, 1418824, 1811250, 2289950, 2869425, 3565926, 4397589, 5384575, 6549215, 7916160, 9512536
Offset: 2

Views

Author

Keywords

Comments

All terms are positive: A093566 >= A054563 ==> C( C(n,2), 3) >= C( C(n,3), 2) ==> n^2*(n^4 + 3n^3 -35n^2 + 69n -38)/144 >= 0 ==> (n - 2)(n - 1)(n^2 + 6n - 19) ==> 0 which it is for all n >= 2.

Crossrefs

Programs

  • Maple
    A093567:=n->binomial(binomial(n, 2), 3) - binomial(binomial(n, 3), 2); seq(A093567(n), n=2..30); # Wesley Ivan Hurt, Feb 02 2014
  • Mathematica
    Table[ Binomial[ Binomial[n, 2], 3] - Binomial[ Binomial[n, 3], 2], {n, 2, 34}]
    LinearRecurrence[{7,-21,35,-35,21,-7,1},{0,1,14,75,265,735,1736},40] (* Harvey P. Dale, Jun 12 2016 *)
  • PARI
    a(n) = binomial(binomial(n,2), 3) - binomial(binomial(n,3), 2); \\ Michel Marcus, Oct 01 2017

Formula

a(n) = A093566(n) - A054563(n).
G.f.: x^3*(-1-7*x+2*x^2+x^3)/(x-1)^7. - R. J. Mathar, Dec 08 2010
Showing 1-3 of 3 results.