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.

A178325 G.f.: A(x) = Sum_{n>=0} x^n/(1-x)^(n^2).

Original entry on oeis.org

1, 1, 2, 6, 21, 83, 363, 1730, 8889, 48829, 284858, 1755325, 11374092, 77208275, 547261631, 4039201624, 30967330941, 246084049137, 2023030659970, 17175765057532, 150367445873108, 1355528352031358, 12566899017130088
Offset: 0

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Author

Paul D. Hanna, Dec 21 2010

Keywords

Comments

Equals the row sums of triangle A214398.
a(n) is the number of weak compositions of n such that if the first part is equal to k then there are a total of k^2 + 1 parts. A weak composition is an ordered partition of the integer n into nonnegative parts. a(3) = 6 because we have: 1+2, 2+0+0+0+1, 2+0+0+1+0, 2+0+1+0+0, 2+1+0+0+0, 3+0+0+0+0+0+0+0+0+0. - Geoffrey Critzer, Oct 09 2013

Examples

			G.f.: A(x) = 1 + x + 2*x^2 + 6*x^3 + 21*x^4 + 83*x^5 + 363*x^6 +...
A(x) = 1 + (x-x^2)*((1-x)-x)/((1-x)^3-x) + (x-x^2)^2*((1-x)-x)*((1-x)^5-x)/(((1-x)^3-x)*((1-x)^7-x)) + (x-x^2)^3*((1-x)-x)*((1-x)^5-x)*((1-x)^9-x)/(((1-x)^3-x)*((1-x)^7-x)*((1-x)^11-x)) +...
		

Crossrefs

Programs

  • Mathematica
    nn=22;CoefficientList[Series[Sum[x^k/(1-x)^(k^2),{k,0,nn}],{x,0,nn}],x]  (* Geoffrey Critzer, Oct 09 2013 *)
  • PARI
    {a(n)=sum(k=0,n,binomial((n-k)^2+k-1,k))}
    
  • PARI
    {a(n)=polcoeff(sum(m=0,n,x^m/(1-x+x*O(x^n))^(m^2)),n)}
    
  • PARI
    {a(n)=polcoeff(sum(m=0,n,(x-x^2)^m*prod(k=1,m,((1-x)^(4*k-3)-x)/((1-x)^(4*k-1)-x +x*O(x^n)))),n)}

Formula

a(n) = Sum_{k=0..n} C((n-k)^2 + k-1, k).
G.f.: A(x) = Sum_{n>=0} (x-x^2)^n*Product_{k=1..n} ((1-x)^(4*k-3) - x)/((1-x)^(4*k-1) - x) due to a q-series identity.
Let q = 1/(1-x), then g.f. A(x) equals the continued fraction:
. A(x) = 1/(1- q*x/(1- q*(q^2-1)*x/(1- q^5*x/(1- q^3*(q^4-1)*x/(1- q^9*x/(1- q^5*(q^6-1)*x/(1- q^13*x/(1- q^7*(q^8-1)*x/(1- ...)))))))))
due to an identity of a partial elliptic theta function.
log(a(n)) ~ n*(log(n) - 2) * (1 + log(4*n) - log((log(n) - 2)*log(n))) / log(n). - Vaclav Kotesovec, Jan 10 2023

A227934 G.f.: Sum_{n>=0} x^n / (1-x)^(n^4).

Original entry on oeis.org

1, 1, 2, 18, 219, 4395, 129280, 4970984, 257765641, 16781325293, 1348125117404, 132465548869248, 15490711962965785, 2134540479514352751, 343307151209151099650, 63606662918084631874716, 13470938654397531939066909, 3238387688528230753569245297, 876825599524773154743990986391
Offset: 0

Views

Author

Paul D. Hanna, Oct 06 2013

Keywords

Examples

			G.f.: A(x) = 1 + x + 2*x^2 + 18*x^3 + 219*x^4 + 4395*x^5 + 129280*x^6 +...
where
A(x) = 1 + x/(1-x) + x^2/(1-x)^16 + x^3/(1-x)^81 + x^4/(1-x)^256 + x^5/(1-x)^625 + x^6/(1-x)^1296 + x^7/(1-x)^2401 +...
		

Crossrefs

Programs

  • PARI
    {a(n)=polcoeff(sum(k=0,n,x^k/(1-x+x*O(x^n))^(k^4)),n)}
    for(n=0,20,print1(a(n),", "))
    
  • PARI
    {a(n)=sum(k=0,n,binomial(k^4+n-k-1, n-k))}
    for(n=0,20,print1(a(n),", "))

Formula

a(n) = Sum_{k=0..n} binomial(k^4 + n-k-1, n-k).

A227935 G.f.: Sum_{n>=0} x^n / (1-x)^(n^5).

Original entry on oeis.org

1, 1, 2, 34, 773, 36656, 3001377, 333647780, 58561139773, 13838291852092, 4280413527001849, 1779704699369214238, 931039792575220097699, 604786686422678514970170, 489307443863919174036440087, 478922652139578822529676247092, 560120417434857039499787289137249
Offset: 0

Views

Author

Paul D. Hanna, Oct 06 2013

Keywords

Examples

			G.f.: A(x) = 1 + x + 2*x^2 + 34*x^3 + 773*x^4 + 36656*x^5 + 3001377*x^6 +...
where
A(x) = 1 + x/(1-x) + x^2/(1-x)^32 + x^3/(1-x)^243 + x^4/(1-x)^1024 + x^5/(1-x)^3125 + x^6/(1-x)^7776 +...
		

Crossrefs

Programs

  • PARI
    {a(n)=polcoeff(sum(k=0,n,x^k/(1-x+x*O(x^n))^(k^5)),n)}
    for(n=0,20,print1(a(n),", "))
    
  • PARI
    {a(n)=sum(k=0,n,binomial(k^5+n-k-1, n-k))}
    for(n=0,20,print1(a(n),", "))

Formula

a(n) = Sum_{k=0..n} binomial(k^5 + n-k-1, n-k).

A230049 Triangle such that the g.f. of column k equals 1/(1-x)^(k^3) for k>=0, as read by rows.

Original entry on oeis.org

1, 0, 1, 0, 1, 1, 0, 1, 8, 1, 0, 1, 36, 27, 1, 0, 1, 120, 378, 64, 1, 0, 1, 330, 3654, 2080, 125, 1, 0, 1, 792, 27405, 45760, 7875, 216, 1, 0, 1, 1716, 169911, 766480, 333375, 23436, 343, 1, 0, 1, 3432, 906192, 10424128, 10668000, 1703016, 58996, 512, 1, 0, 1, 6435, 4272048, 119877472, 275234400, 93240126, 6784540, 131328, 729, 1
Offset: 0

Views

Author

Paul D. Hanna, Oct 06 2013

Keywords

Examples

			Triangle begins:
1;
0, 1;
0, 1, 1;
0, 1, 8, 1;
0, 1, 36, 27, 1;
0, 1, 120, 378, 64, 1;
0, 1, 330, 3654, 2080, 125, 1;
0, 1, 792, 27405, 45760, 7875, 216, 1;
0, 1, 1716, 169911, 766480, 333375, 23436, 343, 1;
0, 1, 3432, 906192, 10424128, 10668000, 1703016, 58996, 512, 1;
0, 1, 6435, 4272048, 119877472, 275234400, 93240126, 6784540, 131328, 729, 1; ...
		

Crossrefs

Cf. A230050 (row sums), A229711.

Programs

  • PARI
    {T(n, k) = polcoeff(1/(1-x+x*O(x^n))^(k^3), n-k)}
    for(n=0,12,for(k=0,n,print1(T(n,k),", "));print(""))
    
  • PARI
    {T(n, k) = binomial(k^3+n-k-1, n-k)}
    for(n=0,12,for(k=0,n,print1(T(n,k),", "));print(""))

Formula

T(n, k) = binomial(k^3+n-k-1, n-k) for n>=k>=0.
Showing 1-4 of 4 results.