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 1-5 of 5 results.

A135081 Column 0 of triangle A135080.

Original entry on oeis.org

1, 1, 2, 8, 50, 436, 4912, 68098, 1122952, 21488640, 468331252, 11456367820, 310888085872, 9269621420284, 301268634277760, 10601062978739338, 401550210033474420, 16291237867482727084, 704847239600911931248
Offset: 0

Views

Author

Paul D. Hanna, Nov 18 2007

Keywords

Comments

Triangle A135080 transforms diagonals in the table of coefficients of successive iterations of x+x^2 (cf. A122888).
Triangle A187005 is defined by: A187005(n,k) = [y^k] R_{n-1}(y+y^2) for k=1..n where R_n(y) is the n-th row polynomial for n>1 with R_1(y)=y.

Links

Crossrefs

Cf. A135080 (triangle); other columns: A135082, A135083.
Cf. A187005, A187006, A187007, A187008, A187009.

Programs

  • PARI
    /* As column 0 of triangle A135080 (slower): */
{a(n)=local(F=x,M,N,P); M=matrix(n+2,n+2,r,c,F=x;for(i=1,r+c-2,F=subst(F,x,x+x^2+x*O(x^(n+2))));polcoeff(F,c)); N=matrix(n+1,n+1,r,c,M[r,c]);P=matrix(n+1,n+1,r,c,M[r+1,c]);(P~*N~^-1)[n+1,1]}
  • PARI
    /* As the main diagonal of triangle A187005 (faster): */
{a(n)=local(Rn=y); for(m=1, n+1, Rn=subst(truncate(Rn), y, y+y^2+y*O(y^m))); polcoeff(Rn/y, n, y)}

Formula

Equals the main diagonal of triangle A187005.

A187005 Triangle, read by rows, where row n equals the coefficients of y^k in R_{n-1}(y+y^2) for k=1..n where R_n(y) is the n-th row polynomial in y for n>1 with R_1(y)=y.

Original entry on oeis.org

1, 1, 1, 1, 2, 2, 1, 3, 6, 8, 1, 4, 12, 29, 50, 1, 5, 20, 69, 202, 436, 1, 6, 30, 134, 538, 1880, 4912, 1, 7, 42, 230, 1164, 5404, 22108, 68098, 1, 8, 56, 363, 2210, 12646, 67092, 315784, 1122952, 1, 9, 72, 539, 3830, 25930, 166520, 997581, 5322126, 21488640, 1
Offset: 1

Views

Author

Paul D. Hanna, Mar 02 2011

Keywords

Comments

Triangles A187115 and A187120 are generated by a similar method, and have main diagonals that are also found in triangle A135080.

Examples

			Triangle begins:
1;
1, 1;
1, 2, 2;
1, 3, 6, 8;
1, 4, 12, 29, 50;
1, 5, 20, 69, 202, 436;
1, 6, 30, 134, 538, 1880, 4912;
1, 7, 42, 230, 1164, 5404, 22108, 68098;
1, 8, 56, 363, 2210, 12646, 67092, 315784, 1122952;
1, 9, 72, 539, 3830, 25930, 166520, 997581, 5322126, 21488640;
1, 10, 90, 764, 6202, 48386, 362556, 2591010, 17337444, 103541022, 468331252; ...
in which rows can be generated as illustrated below.
Row polynomials R_n(y) begin:
R_1(y) = y;
R_2(y) = y + y^2;
R_3(y) = y + 2*y^2 + 2*y^3;
R_4(y) = y + 3*y^2 + 6*y^3 + 8*y^4;
R_5(y) = y + 4*y^2 + 12*y^3 + 29*y^4 + 50*y^5; ...
where row n = the coefficients of y^k in R_{n-1}(y+y^2) for k=1..n;
this method is illustrated by:
n=3: R_2(y+y^2) = (y + 2*y^2 + 2*y^3) + y^4;
n=4: R_3(y+y^2) = (y + 3*y^2 + 6*y^3 + 8*y^4) + 6*y^5 + 2*y^6;
n=5: R_4(y+y^2) = (y + 4*y^2 + 12*y^3 + 29*y^4 + 50*y^5) + 54*y^6 + 32*y^7 + 8*y^8;
where the n-th row polynomial R_n(y) equals R_{n-1}(y+y^2) truncated to the initial n terms.
...
ALTERNATE GENERATING METHOD.
Let F^n(x) denote the n-th iteration of x+x^2 with F^0(x) = x.
Then row n of this triangle may be generated by the coefficients of x^k in G(F^n(x)), k=1..n, where G(x) is the g.f. of A187009:
G(x) = x - x^2 + 2*x^3 - 6*x^4 + 20*x^5 - 80*x^6 + 348*x^7 - 1778*x^8 + 9892*x^9 - 64392*x^10 + 449596*x^11 + 15449192*x^12 +...
and satisfies: [x^(n+1)] G(F^n(x)) = 0 for n>0.
The table of coefficients in G(F^n(x)) begins:
G(x+x^2) : [1, 0, 0, -1, 2, -14, 44, -348, 1476, -14148, ...];
G(F^2(x)): [1, 1, 0, -1, -2, -10, -24, -231, -654, -9276, ...];
G(F^3(x)): [1, 2, 2, 0, -6, -26, -108, -570, -3216, -22622, ...];
G(F^4(x)): [1, 3, 6, 8, 0, -54, -324, -1776, -10594, -71702, ...];
G(F^5(x)): [1, 4, 12, 29, 50, 0, -616, -4846, -32686, -228926, ...];
G(F^6(x)): [1, 5, 20, 69, 202, 436, 0, -8629, -84140, -680298, ...];
G(F^7(x)): [1, 6, 30, 134, 538, 1880, 4912, 0, -143442, -1672428, ..];
G(F^8(x)): [1, 7, 42, 230, 1164, 5404, 22108, 68098, 0, -2762748, ..];
G(F^9(x)): [1, 8, 56, 363, 2210, 12646, 67092, 315784, 1122952, 0, ..]; ...
of which this triangle forms the lower triangular portion.
...
TRANSFORMATIONS OF DIAGONALS BY TRIANGLE A135080.
Given main diagonal = A135081 = [1,1,2,8,50,436,4912,68098,...],
the diagonals can be generated from each other as illustrated by:
_ A135080 * A135081 = A187006 = [1,2,6,29,202,1880,22108,315784,...];
_ A135080 * A187006 = A187007 = [1,3,12,69,538,5404,67092,997581,...];
_ A135080 * A187007 = [1,4,20,134,1164,12646,166520,2591010,...].
Related triangle A135080 begins:
1;
1, 1;
2, 2, 1;
8, 7, 3, 1;
50, 40, 15, 4, 1;
436, 326, 112, 26, 5, 1;
4912, 3492, 1128, 240, 40, 6, 1; ...

Crossrefs

Cf. diagonals: A135081, A187006, A187007; row sums: A187008.
Cf. A187009, A135080, A187115, A187120.

Programs

  • Mathematica
    f[p_] := Series[p /. y -> y + y^2, {y, 0, 1 + Exponent[p, y]}] // Normal;
Flatten[ Rest[ CoefficientList[#, y]] & /@ NestList[f, y, 10]][[1 ;; 56]] (* Jean-François Alcover, Jun 09 2011 *)
  • PARI
    {T(n,k)=local(Rn=y);for(m=1,n,Rn=subst(truncate(Rn),y,y+y^2+y*O(y^m)));polcoeff(Rn,k,y)}
for(n=1,10,for(k=1,n,print1(T(n,k),", "));print(""))
  • PARI
    {T(n,k)=if(k>n||k<1,0,if(n==1,1,sum(j=k\2,k,binomial(j,k-j)*T(n-1,j))))}
for(n=1,10,for(k=1,n,print1(T(n,k),", "));print(""))

Formula

T(n,k) = Sum_{j=[k/2],k} C(j,k-j)*T(n-1,j) for n>=k>1 with T(n,1)=1 and T(n,k)=0 when k>n or k<1.
Main diagonal equals column 0 of triangle A135080, which transforms diagonals in the table of coefficients of the iterations of x+x^2.
Triangle A135080 also transforms diagonals in this triangle into each other.
Diagonal m of this triangle equals column 0 of the m-th power of triangle A135080, with diagonal m=1 being the main diagonal.

A187009 G.f. A(x) satisfies: [x^(n+1)] A(F^n(x)) = 0 for n>0 where F^n(x) denotes the n-th iteration of F(x) = x+x^2 with F^0(x)=x.

Original entry on oeis.org

1, -1, 2, -6, 20, -80, 348, -1778, 9892, -64392, 449596, -3609782, 30152616, -284037468, 2694480888, -28592860322, 295151311376, -3440953545088, 37165311149276, -471576198145144, 5062381083026352, -71104461751595892
Offset: 1

Views

Author

Paul D. Hanna, Mar 02 2011

Keywords

Examples

			G.f.: A(x) = x - x^2 + 2*x^3 - 6*x^4 + 20*x^5 - 80*x^6 + 348*x^7 +...
Let F^n(x) denote the n-th iteration of F(x) = x+x^2 with F^0(x)=x,
then the table of coefficients in A(F^n(x)), n>=0, begins:
[1, -1, 2, -6, 20, -80, 348, -1778, 9892, -64392, ...];
[1, 0, 0, -1, 2, -14, 44, -348, 1476, -14148, 73920, ...];
[1, 1, 0, -1, -2, -10, -24, -231, -654, -9276, -32456, ...];
[1, 2, 2, 0, -6, -26, -108, -570, -3216, -22622, -162596, ...];
[1, 3, 6, 8, 0, -54, -324, -1776, -10594, -71702, -540448, ...];
[1, 4, 12, 29, 50, 0, -616, -4846, -32686, -228926, -1749972, ...];
[1, 5, 20, 69, 202, 436, 0, -8629, -84140, -680298, -5508864, ...];
[1, 6, 30, 134, 538, 1880, 4912, 0, -143442, -1672428, -15821492, ...];
[1, 7, 42, 230, 1164, 5404, 22108, 68098, 0, -2762748, -37526484, ...];
[1, 8, 56, 363, 2210, 12646, 67092, 315784, 1122952, 0, -60534272, ..];
[1, 9, 72, 539, 3830, 25930, 166520, 997581, 5322126, 21488640, 0, ..]; ...
in which the main diagonal equals all zeros after the initial '1';
the lower triangular portion of the above table forms triangle A187005.

Crossrefs

Cf. A187005, A135080, A122888, A135081, A187006, A187007, A187008.

Programs

  • PARI
    {ITERATE(F,n,p)=local(G=x);for(i=1,n,G=subst(F,x,G+x*O(x^p)));G}
{a(n)=local(A=[1]);for(i=1,n,A=concat(A,0);A[#A]=-Vec(subst(x*Ser(A),x,ITERATE(x+x^2,i,#A)))[#A]);A[n]}

A187008 Row sums of triangle A187005.

Original entry on oeis.org

1, 2, 5, 18, 96, 733, 7501, 97054, 1521112, 28005248, 592218737, 14141289480, 376251253450, 11036022346816, 353747961265089, 12301349824260074, 461216257715290976, 18545829116907146812, 796122011317944176206
Offset: 1

Views

Author

Paul D. Hanna, Mar 02 2011

Keywords

Comments

Definition of triangle: A187005(n,k) = [y^k] R_{n-1}(y+y^2) for k=1..n where R_n(y) is the n-th row polynomial for n>1 with R_1(y)=y.

Crossrefs

Cf. A187005, A135081, A187006, A187007, A187009.

A187006 A diagonal of triangle A187005.

Original entry on oeis.org

1, 2, 6, 29, 202, 1880, 22108, 315784, 5322126, 103541022, 2285965792, 56501970700, 1546339364952, 46433615292128, 1518172222889000, 53695946069029290, 2042960241832903824, 83207255745283689726, 3612360848988984098484, 166537270023045091100852, 8125771150231992039148508
Offset: 1

Views

Author

Paul D. Hanna, Mar 02 2011

Keywords

Comments

Definition of triangle: A187005(n,k) = [y^k] R_{n-1}(y+y^2) for k=1..n where R_n(y) is the n-th row polynomial for n>1 with R_1(y)=y.

Crossrefs

Cf. A187005, A135081, A187007, A187008, A187009.

Programs

  • PARI
    {a(n)=local(Rn=y);for(m=1,n+1,Rn=subst(truncate(Rn),y,y+y^2+y*O(y^m)));polcoeff(Rn,n,y)}

Extensions

More terms from Michel Marcus, Feb 01 2025
Showing 1-5 of 5 results.

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