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 1-8 of 8 results.

A060543 Triangle, read by antidiagonals, where T(n,k) = C(n+n*k+k, n*k+k).

Original entry on oeis.org

1, 1, 1, 1, 3, 1, 1, 10, 5, 1, 1, 35, 28, 7, 1, 1, 126, 165, 55, 9, 1, 1, 462, 1001, 455, 91, 11, 1, 1, 1716, 6188, 3876, 969, 136, 13, 1, 1, 6435, 38760, 33649, 10626, 1771, 190, 15, 1, 1, 24310, 245157, 296010, 118755, 23751, 2925, 253, 17, 1, 1, 92378, 1562275
Offset: 0

Views

Author

Henry Bottomley, Apr 02 2001

Keywords

Comments

Main diagonal is A108288. Antidiagonal sums is A108289. Inverse binomial transforms of each row give triangle A108290. G.f. of row n multiplied by (1-x)^(n+1) equals g.f. of row n of triangle A108267 (rows sums of A108267 equal (n+1)^n).

Examples

			row 1: (2*n+1)/1!
row 2: (3*n+1)*(3*n+2)/2!
row 3: (4*n+1)*(4*n+2)*(4*n+3)/3!
row 4: (5*n+1)*(5*n+2)*(5*n+3)*(5*n+4)/4!
row 5: (6*n+1)*(6*n+2)*(6*n+3)*(6*n+4)*(6*n+5)/5!.
Table begins:
1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,...
1,3,5,7,9,11,13,15,17,19,21,23,25,27,...
1,10,28,55,91,136,190,253,325,406,496,...
1,35,165,455,969,1771,2925,4495,6545,...
1,126,1001,3876,10626,23751,46376,82251,...
1,462,6188,33649,118755,324632,749398,...
1,1716,38760,296010,1344904,4496388,...
		

Crossrefs

Cf. A108290, A108267, A108288, A108289, A060544 (row 2), A015219 (row 3).
Rows include A000012, A001700, A025174. Columns include A000012, A005408, A060544. Main diagonal is A060545.

Programs

  • PARI
    T(n,k)=binomial(n+n*k+k,n*k+k)
    
  • PARI
    { i=0; write("b060543.txt", "0 1"); for (m=0, 20, for (k=0, m + 1, n=m - k + 1; write("b060543.txt", i++, " ", binomial(n + n*k + k, n*k + k))); ) } \\ Harry J. Smith, Jul 06 2009

Formula

a(n) = A060539(n, k)/n = A007318(nk, k)/n = A060540(n, k)/A060540(n-1, k).

Extensions

Entry revised by Paul D. Hanna, May 31 2005
Edited by N. J. A. Sloane at the suggestion of Andrew S. Plewe, Jun 17 2007

A177784 a(n) = binomial(n^2, n) / ( n*(n+1) ).

Original entry on oeis.org

1, 7, 91, 1771, 46376, 1533939, 61474519, 2898753715, 157366449604, 9672348219898, 664226242466073, 50419551102990876, 4193002458968329488, 379189865879906158731, 37054233830964389244975
Offset: 2

Views

Author

Michel Lagneau, May 13 2010

Keywords

Comments

All terms are integer because n and n+1 divide the binomial (cf. A060545, A177234).
Empirical: In the ring of symmetric functions over the fraction field Q(q, t), letting s(n) denote the Schur function indexed by n, a(n)*(-1)^(n+1) is equal to the coefficient of s(n) in nabla^(n)s(n) with q=t=1, where nabla denotes the "nabla operator" on symmetric functions. - John M. Campbell, Nov 18 2017

Examples

			For n = 3, binomial(9,3)/(3*4) =84/12 = 7.
For example, the coefficient of s(3) in nabla(nabla(nabla(s(3)))) is equal to q^6*t^2+q^5*t^3+q^4*t^4+q^3*t^5+q^2*t^6+q^4*t^3+q^3*t^4, and if we let q and t be equal to 1, this coefficient reduces to 7 = a(3). - _John M. Campbell_, Nov 18 2017
		

Crossrefs

Programs

  • Magma
    [Binomial(n^2,n)/(2*Binomial(n+1,2)): n in [2..30]]; // G. C. Greubel, Jul 18 2024
    
  • Maple
    A177784 := proc(n)
            binomial(n^2,n)/(n^2+n) ;
    end proc:
    seq(A177784(n),n=2..20) ; # R. J. Mathar, Nov 07 2011
  • Mathematica
    Table[Binomial[n^2,n]/(2*Binomial[n+1,2]), {n,2,30}] (* G. C. Greubel, Jul 18 2024 *)
  • SageMath
    [binomial(n^2,n)//(n*(n+1)) for n in range(2,31)] # G. C. Greubel, Jul 18 2024

A177456 a(n) = binomial(n^2,n+1)/n.

Original entry on oeis.org

2, 42, 1092, 35420, 1391280, 64425438, 3442573064, 208710267480, 14162980464360, 1063958304188780, 87677864005521636, 7865449972066576656, 763126447532235966816, 79629871834780293333510
Offset: 2

Views

Author

Michel Lagneau, May 09 2010

Keywords

Comments

n divides binomial(n^2,n+1).
Proof 1 :(n+1)*binomial(n^2,n+1) = n*(n-1)*binomial(n^2,n) => n divide binomial(n^2,n+1) because gcd(n,n+1) = 1.
Proof 2 : a(n) = binomial(n^2,n+1)/n = (n-1)*binomial(n^2-2,n-1)=> a(n) is an integer. - Michel Lagneau, May 13 2010

Examples

			For n=4, 1092 is in the sequence because binomial(16,5)/4 = 4368/4 = 1092.
		

Crossrefs

Programs

  • Magma
    [Binomial(n^2,n+1)/n: n in [2..30]]; // G. C. Greubel, Apr 29 2024
    
  • Maple
    with(numtheory):n0:=30:T:=array(1..n0-1):for n from 2 to n0 do:T[n-1]:= (binomial(n*n,n+1))/n:od:print(T):
  • Mathematica
    Table[Binomial[n^2,n+1]/n, {n,2,30}] (* G. C. Greubel, Apr 29 2024 *)
  • SageMath
    [binomial(n^2,n+1)/n for n in range(2,31)] # G. C. Greubel, Apr 29 2024

Formula

a(n) = binomial(n^2,n+1)/n.
From G. C. Greubel, Apr 29 2024: (Start)
a(n) = (n-1)*A177234(n).
a(n) = (n-1)*A177788(n)/n.
a(n) = n*(n-1)*A177784(n).
a(n) = A014062(n)/n. (End)

A177788 a(n) = binomial(n^2, n+1)/(n-1).

Original entry on oeis.org

4, 63, 1456, 44275, 1669536, 75163011, 3934369216, 234799050915, 15736644960400, 1170354134607658, 95648578915114512, 8520904136405458044, 821828481957792579648, 85317719822978885714475, 9485883860726883646713600, 1124586875214241546178986915
Offset: 2

Views

Author

Michel Lagneau, May 13 2010

Keywords

Comments

The entries are integer for n >= 2 because binomial(n^2,n+1)/(n-1) = n*binomial(n^2-2,n-1), which is a product of two integers.

Crossrefs

Programs

  • Magma
    [Binomial(n^2,n+1)/(n-1): n in [2..30]]; // G. C. Greubel, Apr 28 2024
    
  • Maple
    n0:=30: T:=array(1..n0): T:=array(1..n0-1): for n from 2 to n0 do: T[n-1]:= (binomial(n^2,n+1))/(n-1): od: print(T):
  • Mathematica
    Table[Binomial[n^2,n+1]/(n-1), {n,2,40}] (* G. C. Greubel, Apr 28 2024 *)
  • PARI
    a(n) = binomial(n^2, n+1)/(n-1) \\ Charles R Greathouse IV, May 01 2024
  • SageMath
    [binomial(n^2,n+1)/(n-1) for n in range(2,31)] # G. C. Greubel, Apr 28 2024
    

Formula

a(n) = binomial(n^2,n+1)/(n-1).
a(n) = n * A177234(n).
a(n) = n^2 * A177784(n).

Extensions

Removed redundant second Maple version - R. J. Mathar, May 14 2010

A177454 ( binomial(2*p,p) - 2)/p where p = prime(n).

Original entry on oeis.org

2, 6, 50, 490, 64130, 800046, 137270954, 1860277042, 357975249026, 1036802293087622, 15013817846943906, 47192717955016924590, 10360599532897359064118, 154361699651715243559786
Offset: 1

Views

Author

Michel Lagneau, May 09 2010

Keywords

Comments

All entries are integer because binomial(2p, p) == 2 (mod p). [Proof: p!*binomial(2p, p) = 2p(2p - 1)(2p - 2) ... (p + 1) .
Therefore (p - 1)!*binomial(2p, p) = 2(2p - 1) ... (p + 1) == 2(p - 1)! (mod p).
Since p is prime: (p - 1)! <> 0 (mod p). Because Z/pZ is a finite field, we conclude that binomial(2p, p) == 2 (mod p).]

Examples

			a(1) = 2 because prime(1) = 2 and (binomial(4, 2) - 2)/2 = (6 - 2)/2 = 2.
a(4) = 490 because prime(4) = 7 and (binomial(14, 7) - 2)/7 = (3432 - 2)/7 = 490.
		

Crossrefs

Programs

  • Magma
    [(Binomial(2*p,p)-2)/p where p is NthPrime(n):n in [1..14]]; // Marius A. Burtea, Aug 11 2019
  • Maple
    with(numtheory): n0:=20: T:=array(1..n0): k:=1: for n from 1 to 72 do:if type(n,prime)=true then T[k]:= (binomial(2*n,n)-2)/n: k:=k+1: fi: od: print(T):
  • Mathematica
    Table[(Binomial[2Prime[n], Prime[n]] - 2)/Prime[n], {n, 15}] (* Alonso del Arte, Feb 27 2013 *)

Formula

a(n) = (A000984(p) - 2) / p with p = A000040(n).

A303143 Number of minimum total dominating sets in the n-transposition graph.

Original entry on oeis.org

0, 1, 9, 784, 3686400
Offset: 1

Views

Author

Eric W. Weisstein, Apr 19 2018

Keywords

Comments

a(n) matches all 4 terms of the finite sequence A168257(n).
a(n) matches A060545(n-1)^2 for n=2 to 4.
All terms are squares (see comment in A303146). - Andrew Howroyd, Jun 11 2025

Crossrefs

Cf. A303146, A303150 (set size), A321618.

Extensions

a(5) from Christian Sievers, Jun 25 2025

A108288 Main diagonal of table A060543; a(n) = C((n+1)^2-1, n*(n+1)).

Original entry on oeis.org

1, 3, 28, 455, 10626, 324632, 12271512, 553270671, 28987537150, 1731030945644, 116068178638776, 8634941152058949, 705873715441872264, 62895036884524942320, 6067037854078498539696, 629921975126394617164575, 70043473196734767582082230
Offset: 0

Views

Author

Paul D. Hanna, May 31 2005

Keywords

Crossrefs

Programs

  • PARI
    a(n)=binomial((n+1)^2-1,n*(n+1))

Formula

a(n) = A060545(n+1). - R. J. Mathar, Aug 24 2008

A177466 a(n) = binomial(n^3, n^2) / (n^2 + n + 1).

Original entry on oeis.org

10, 360525, 23263187479980, 4195317468983232014706855, 3118254010126197540790713959812283024388, 13329519847131745416659896296893907619682838146506167497550
Offset: 2

Views

Author

Michel Lagneau, May 09 2010

Keywords

Comments

All entries are integers. [Proof: binomial(n^3, n^2) / (n^2 + n + 1) = n^3 (n^3 - 1) (n^3 - 2)*...*(n^3- n^2 +1) / ( (n^2)! *(n^2 + n + 1)). With n^3 - 1 = (n-1)*(n^2 + n + 1), we obtain a(n) = n* binomial(n^3-2, n^2-2) / (n+1). Finally: (n+1) * binomial(n^3, n^2) * 1/ (n^2 + n + 1) = n*binomial(n^3-2, n^2-2). QED]
The step after "finally" seems to demonstrate merely that (n+1)*a(n) is an integer, but not that a(n) is itself an integer. Is the proof incomplete? - R. J. Mathar, Dec 06 2010
So far all that has been shown is that (n+1)*a(n) is an integer. To complete the proof, note that a(n) = n^3*(n-1)*(n^3-2)*...*(n^3-n^2) / (n^2*(n^2-1)!*(n^3-n^2)) = binomial(n^3-2,n^2-1)/n. Hence n*a(n) is also an integer, and so (n+1)*a(n) - n*a(n) = a(n) is an integer. Q.E.D. - N. J. A. Sloane, Dec 09 2010

Examples

			For n = 2, a(2) = binomial(8,4)/7 = 70/7 = 10.
		

Crossrefs

Programs

  • Magma
    [Binomial(n^3,n^2)/(n^2+n+1): n in [2..12]]; // G. C. Greubel, Jul 18 2024
    
  • Maple
    A177466 := proc(n) binomial(n^3,n^2)/(n^2+n+1); end proc:
    seq(A177466(n),n=2..10) ; # R. J. Mathar, Dec 06 2010
  • Mathematica
    Table[Binomial[n^3,n^2]/(n^2+n+1),{n,2,7}] (* Harvey P. Dale, Jan 24 2019 *)
  • SageMath
    [binomial(n^3,n^2)/(n^2+n+1) for n in range(2,13)] # G. C. Greubel, Jul 18 2024
Showing 1-8 of 8 results.