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 1-7 of 7 results.

A119370 G.f. satisfies A(x) = 1 + x*A(x)^2 + x^2*(A(x)^2 - A(x)).

Original entry on oeis.org

1, 1, 2, 6, 19, 64, 225, 816, 3031, 11473, 44096, 171631, 675130, 2679728, 10719237, 43168826, 174885089, 712222799, 2914150406, 11973792218, 49385167369, 204386777160, 848530495383, 3532844222611, 14747626307436, 61712139464939
Offset: 0

Views

Author

Paul D. Hanna, May 16 2006

Keywords

Comments

Equals base sequence of pendular trinomial triangle A119369; iterated convolutions of this sequence with the central terms (A119371) generates all diagonals of A119369. For example: A119372 = A119370 * A119371; A119373 = A119370^2 * A119371.
Diagonal sums of number array A133336. - Philippe Deléham, Nov 09 2009

Examples

			A(x) = 1 + x + 2*x^2 + 6*x^3 + 19*x^4 + 64*x^5 + 225*x^6 + 816*x^7 +...
x*A(x)^2 = x + 2*x^2 + 5*x^3 + 16*x^4 + 54*x^5 + 190*x^6 + 690*x^7 +...
x^2*( A(x)^2 - A(x) ) = 1*x^3 + 3*x^4 + 10*x^5 + 35*x^6 + 126*x^7 +...
		

Crossrefs

Programs

  • Magma
    R:=PowerSeriesRing(Rationals(), 30);
    Coefficients(R!( (1+x^2 -Sqrt(1-4*x-2*x^2+x^4))/(2*x*(1+x)) )); // G. C. Greubel, Mar 17 2021
  • Maple
    m:= 30;
    S:= series( (1+x^2 -sqrt(1-4*x-2*x^2+x^4))/(2*x*(1+x)), x, m+1);
    seq(coeff(S, x, j), j = 0..m); # G. C. Greubel, Mar 17 2021
  • Mathematica
    CoefficientList[Series[((1+x^2)-Sqrt[(1+x^2)^2-4*x*(1+x)])/(2*x*(1+x)), {x, 0, 20}], x] (* Vaclav Kotesovec, Sep 11 2013 *)
  • PARI
    {a(n)=polcoeff(2/((1+x^2)+sqrt((1+x^2)^2-4*x*(1+x)+x*O(x^n))),n)}
    
  • Sage
    def A119370_list(prec):
        P. = PowerSeriesRing(QQ, prec)
        return P( (1+x^2 -sqrt(1-4*x-2*x^2+x^4))/(2*x*(1+x)) ).list()
    A119370_list(30) # G. C. Greubel, Mar 17 2021
    

Formula

G.f.: A(x) = ((1+x^2) - sqrt( (1+x^2)^2 - 4*x*(1+x) ))/(2*x*(1+x)). Equals the inverse binomial transform of A104547.
Recurrence: (n+1)*a(n) = 3*(n-1)*a(n-1) + 6*(n-1)*a(n-2) + 2*(n-2)*a(n-3) - (n-5)*a(n-4) - (n-5)*a(n-5). - Vaclav Kotesovec, Sep 11 2013
a(n) ~ sqrt(-z^2-3*z+1)*(4+2*z-z^3)^(n+1)*(-z^3+z^2+z+3) / (8*sqrt(Pi) * n^(3/2)), where z = 1/(2*sqrt(3/(4+(280-24*sqrt(129))^(1/3) + 2*(35 + 3*sqrt(129))^(1/3)))) - 1/2*sqrt(8/3-1/3*(280-24*sqrt(129))^(1/3) - 2/3*(35+3*sqrt(129))^(1/3) + 8*sqrt(3/(4+(280-24*sqrt(129))^(1/3) + 2*(35 + 3*sqrt(129))^(1/3)))) = 0.225270426... is the root of the equation 1-2*z^2+z^4-4*z=0. - Vaclav Kotesovec, Sep 11 2013
G.f.: 1/G(0) where G(k) = 1 - q/(1 - (q + q^2) / G(k+1) ). - Joerg Arndt, Dec 06 2014
a(n) = Sum_{k=0..floor(n/2)} binomial(n-k-1,k) * binomial(2*n-3*k+1,n-2*k)/(2*n-3*k+1). - Seiichi Manyama, Aug 28 2023
Conjecture: A(x) = 1 + x*exp(Sum_{n >= 1} g(n, x)*x^n/n), where g(n, x) = Sum_{k = 0..n} binomial(n, k)^2*(1 + x)^k. Cf. A105633 and A167638. - Peter Bala, Sep 10 2024

A119369 Pendular trinomial triangle, read by rows of 2n+1 terms (n>=0), defined by the recurrence: if 0 < k < n, T(n,k) = T(n-1,k) + T(n,2n-1-k); otherwise, if n-1 < k < 2n-1, T(n,k) = T(n-1,k) + T(n,2n-2-k); with T(n,0)=T(n+1,2n)=1 and T(n+1,2n+1)=T(n+1,2n+2)=0.

Original entry on oeis.org

1, 1, 0, 0, 1, 1, 1, 0, 0, 1, 2, 3, 2, 1, 0, 0, 1, 3, 6, 9, 7, 3, 1, 0, 0, 1, 4, 10, 20, 30, 23, 11, 4, 1, 0, 0, 1, 5, 15, 36, 70, 104, 81, 40, 16, 5, 1, 0, 0, 1, 6, 21, 58, 133, 253, 374, 293, 149, 63, 22, 6, 1, 0, 0, 1, 7, 28, 87, 226, 501, 938, 1380, 1087, 564, 248, 93, 29, 7, 1, 0, 0
Offset: 0

Views

Author

Paul D. Hanna, May 16 2006

Keywords

Comments

The diagonals may be generated by iterated convolutions of a base sequence B with the sequence C of central terms. The g.f. B(x) of the base sequence satisfies: B = 1 + x*B^2 + x^2*(B^2 - B); the g.f. C(x) of the central terms satisfies: C(x) = 1/(1+x - x*B(x)).

Examples

			To obtain row 4, pendular sums of row 3 are carried out as follows.
  [1, 2, 3, 2, 1, 0, 0]: given row 3;
  [1, _, _, _, _, _, _]: start with T(4,0) = T(3,0) = 1;
  [1, _, _, _, _, _, 1]: T(4,6) = T(4,0) + T(3,6) = 1 + 0 = 1;
  [1, 3, _, _, _, _, 1]: T(4,1) = T(4,6) + T(3,1) = 1 + 2 = 3;
  [1, 3, _, _, _, 3, 1]: T(4,5) = T(4,1) + T(3,5) = 3 + 0 = 3;
  [1, 3, 6, _, _, 3, 1]: T(4,2) = T(4,5) + T(3,2) = 3 + 3 = 6;
  [1, 3, 6, _, 7, 3, 1]: T(4,4) = T(4,2) + T(3,4) = 6 + 1 = 7;
  [1, 3, 6, 9, 7, 3, 1]: T(4,3) = T(4,4) + T(3,3) = 7 + 2 = 9;
  [1, 3, 6, 9, 7, 3, 1, 0, 0]: complete row 4 by appending two zeros.
Triangle begins:
  1;
  1, 0,  0;
  1, 1,  1,  0,   0;
  1, 2,  3,  2,   1,   0,   0;
  1, 3,  6,  9,   7,   3,   1,    0,    0;
  1, 4, 10, 20,  30,  23,  11,    4,    1,   0,   0;
  1, 5, 15, 36,  70, 104,  81,   40,   16,   5,   1,  0,  0;
  1, 6, 21, 58, 133, 253, 374,  293,  149,  63,  22,  6,  1, 0, 0;
  1, 7, 28, 87, 226, 501, 938, 1380, 1087, 564, 248, 93, 29, 7, 1, 0, 0;
Central terms are:
  C = A119371 = [1, 0, 1, 2, 7, 23, 81, 293, 1087, 4110, ...].
Lower diagonals start:
  D1 = A119372 = [1, 1, 3, 9, 30, 104, 374, 1380, 5197, ...];
  D2 = A119373 = [1, 2, 6, 20, 70, 253, 938, 3546, 13617, ...].
  Diagonals above central terms (ignoring leading zeros) start:
  U1 = A119375 = [1, 3, 11, 40, 149, 564, 2166, 8420, ...];
  U2 = A119376 = [1, 4, 16, 63, 248, 980, 3894, 15563, ...].
There exists the base sequence:
  B = A119370 = [1, 1, 2, 6, 19, 64, 225, 816, 3031, 11473, ...]
which generates all diagonals by convolutions with central terms:
  D2 = B * D1 = B^2 * C
  U2 = B * U1 = B^2 * C"
where C" = [1, 2, 7, 23, 81, 293, 1087, ...]
are central terms not including the initial [1,0].
		

Crossrefs

Programs

  • Maple
    T:= proc(n, k) option remember;
          if k=0 and n=0 then 1
        elif k<0 or k>2*(n-1) then 0
        elif n=2 and k<3 then 1
        else T(n-1, k) + `if`(kG. C. Greubel, Mar 16 2021
  • Mathematica
    T[n_, k_]:= T[n, k]= If[n==0 && k==0, 1, If[k<0 || k>2*(n-1), 0, If[n==2 && k<3, 1, T[n-1, k] +If[kG. C. Greubel, Mar 16 2021 *)
  • PARI
    T(n,k)= if(k==0 && n==0, 1, if(k>2*n-2 || k<0, 0, if(n==2 && k<=2, 1, T(n-1,k) + if(k
    				
  • Sage
    @CachedFunction
    def T(n, k):
        if (n==0 and k==0): return 1
        elif (k<0 or k>2*(n-1)): return 0
        elif (n==2 and k<3): return 1
        else: return T(n-1, k) + ( T(n, 2*n-k-1) if kG. C. Greubel, Mar 16 2021

Formula

Sum_{k=0..2*n} T(n, k) = A119372(n). - G. C. Greubel, Mar 16 2021

A119371 G.f. satisfies: A(x) = (1+x) - x*(4+x)*A(x) + x*(3+2*x)*A(x)^2.

Original entry on oeis.org

1, 0, 1, 2, 7, 23, 81, 293, 1087, 4110, 15783, 61387, 241329, 957400, 3828055, 15410651, 62410871, 254095382, 1039394147, 4269718110, 17606507789, 72852976317, 302403773303, 1258855723796, 5254253027485, 21983753239135
Offset: 0

Views

Author

Paul D. Hanna, May 17 2006

Keywords

Comments

Equals central terms of pendular trinomial triangle A119369.

Examples

			            A(x) = 1 + x^2 + 2*x^3 + 7*x^4 + 23*x^5 + 81*x^6 ...;
   -x*(4+x)*A(x) = -4*x -x^2 -4*x^3 -9*x^4 -30*x^5 -99*x^6 - ...;
x*(3+2*x)*A(x)^2 = 3*x +2*x^2 +6*x^3 +16*x^4 +53*x^5 +180*x^6 + ...;
		

Crossrefs

Programs

  • Magma
    R:=PowerSeriesRing(Rationals(), 30);
    Coefficients(R!( (1+4*x+x^2 -Sqrt(1-4*x-2*x^2+x^4))/(2*x*(3+2*x)) )); // G. C. Greubel, Mar 17 2021
  • Maple
    m:= 30;
    S:= series( (1+4*x+x^2 -sqrt(1-4*x-2*x^2+x^4))/(2*x*(3+2*x)), x, m+1);
    seq(coeff(S, x, j), j = 0..m); # G. C. Greubel, Mar 17 2021
  • Mathematica
    CoefficientList[Series[(1+4*x+x^2-Sqrt[(1+4*x+x^2)^2-4*x*(1+x)*(3+2*x)])/(2*x*(3+2*x)), {x, 0, 20}], x] (* Vaclav Kotesovec, Sep 11 2013 *)
  • PARI
    {a(n)=polcoeff((2*(1+x))/(1+4*x+x^2+sqrt((1+4*x+x^2)^2-4*x*(1+x)*(3+2*x)+x*O(x^n))),n)}
    
  • Sage
    def A119371_list(prec):
        P. = PowerSeriesRing(QQ, prec)
        return P( (1+4*x+x^2 -sqrt(1-4*x-2*x^2+x^4))/(2*x*(3+2*x)) ).list()
    A119371_list(30) # G. C. Greubel, Mar 17 2021
    

Formula

G.f.: A(x) = (1+4*x+x^2 - sqrt((1+4*x+x^2)^2 - 4*x*(1+x)*(3+2*x)))/(2*x*(3+2*x)).
G.f.: A(x) = 1/(1+x - x*B(x)) = (1 + x*H(x))/(1+x) = 1 + x^2*F(x)/B(x), where B(x) is g.f. of A119370, H(x) is g.f. of A119372, F(x) is g.f. of A119375.
Recurrence: 3*(n+1)*a(n) = 2*(5*n-4)*a(n-1) + 2*(7*n-8)*a(n-2) + 4*(n-2)*a(n-3) - 3*(n-5)*a(n-4) - 2*(n-5)*a(n-5). - Vaclav Kotesovec, Sep 11 2013
a(n) ~ sqrt(-z^2-3*z+1)*(4+2*z-z^3)^(n+1)*(35-8*z^3+12*z^2-2*z) /(242*sqrt(Pi)*n^(3/2)), where z = 1/(2*sqrt(3/(4+(280-24*sqrt(129))^(1/3) + 2*(35+3*sqrt(129))^(1/3)))) - 1/2*sqrt(8/3-1/3*(280-24*sqrt(129))^(1/3) - 2/3*(35+3*sqrt(129))^(1/3) + 8*sqrt(3/(4+(280-24*sqrt(129))^(1/3) + 2*(35+3*sqrt(129))^(1/3)))) = 0.225270426... is the root of the equation 1-2*z^2+z^4-4*z=0. - Vaclav Kotesovec, Sep 11 2013

A119373 A lower diagonal of pendular trinomial triangle A119369.

Original entry on oeis.org

1, 2, 6, 20, 70, 253, 938, 3546, 13617, 52967, 208255, 826315, 3304456, 13304924, 53891402, 219442686, 897772983, 3688451380, 15211545938, 62950542636, 261329456566, 1087985751336, 4541524025769, 19003488710465, 79696345430789
Offset: 0

Views

Author

Paul D. Hanna, May 17 2006

Keywords

Crossrefs

Programs

  • Magma
    R:=PowerSeriesRing(Rationals(), 30);
    Coefficients(R!( 8*(1+x)/( ((1+x^2) +Sqrt((1+x^2)^2 -4*x*(1+x)))^2*(1+4*x+x^2 +Sqrt((1+4*x+x^2)^2 -4*x*(1+x)*(3+2*x))) ) )); // G. C. Greubel, Mar 16 2021
  • Mathematica
    CoefficientList[Series[8*(1+x)/( ((1+x^2) + Sqrt[(1+x^2)^2 -4*x*(1+x)])^2*(1 + 4*x +x^2 +Sqrt[(1+4*x+x^2)^2 -4*x*(1+x)*(3+2*x)])), {x,0,30}], x] (* G. C. Greubel, Mar 16 2021 *)
  • PARI
    {a(n)=polcoeff(8*(1+x)/((1+x^2)+sqrt((1+x^2)^2-4*x*(1+x)+x*O(x^n)))^2 /(1+4*x+x^2 + sqrt((1+4*x+x^2)^2 - 4*x*(1+x)*(3+2*x)+x*O(x^n))),n)}
    
  • Sage
    def A119373_list(prec):
        P. = PowerSeriesRing(QQ, prec)
        return P( 8*(1+x)/( ((1+x^2) +sqrt((1+x^2)^2 -4*x*(1+x)))^2*(1+4*x+x^2 +sqrt((1+4*x+x^2)^2 -4*x*(1+x)*(3+2*x))) ) ).list()
    A119373_list(30) # G. C. Greubel, Mar 16 2021
    

Formula

G.f.: A(x) = B(x)^2/(1+x - x*B(x)) = B(x)^2*G(x) = B(x)*H(x), where B(x) is g.f. of A119370, G(x) is g.f. of A119371 and H(x) is g.f. of A119372.
G.f.: 8*(1+x)/( ((1+x^2) +sqrt((1+x^2)^2 -4*x*(1+x)))^2*(1+4*x+x^2 +sqrt((1+4*x+x^2)^2 -4*x*(1+x)*(3+2*x))) ).

A119374 A lower diagonal of pendular trinomial triangle A119369.

Original entry on oeis.org

1, 3, 10, 36, 133, 501, 1918, 7440, 29180, 115522, 461044, 1852938, 7492846, 30464306, 124461782, 510696350, 2103708187, 8696498477, 36066269640, 150015248758, 625664295594, 2615929689642, 10962436020878, 46037427169060
Offset: 0

Views

Author

Paul D. Hanna, May 17 2006

Keywords

Crossrefs

Programs

  • Magma
    R:=PowerSeriesRing(Rationals(), 30);
    Coefficients(R!( 16*(1+x)/( ((1+x^2) +Sqrt((1+x^2)^2-4*x*(1+x)))^3*(1+4*x+x^2 +Sqrt((1+4*x+x^2)^2 - 4*x*(1+x)*(3+2*x))) ) )); // G. C. Greubel, Mar 16 2021
  • Mathematica
    CoefficientList[Series[16*(1+x)/( ((1+x^2) +Sqrt[(1+x^2)^2 -4*x*(1+x)])^3*(1+4*x +x^2 +Sqrt[(1+4*x+x^2)^2 -4*x*(1+x)*(3+2*x)])), {x,0,30}], x] (* G. C. Greubel, Mar 16 2021 *)
  • PARI
    {a(n)=polcoeff(16*(1+x)/((1+x^2)+sqrt((1+x^2)^2-4*x*(1+x)+x*O(x^n)))^3 /(1+4*x+x^2 + sqrt((1+4*x+x^2)^2 - 4*x*(1+x)*(3+2*x)+x*O(x^n))),n)}
    
  • Sage
    def A119374_list(prec):
        P. = PowerSeriesRing(QQ, prec)
        return P( 16*(1+x)/( ((1+x^2) +sqrt((1+x^2)^2-4*x*(1+x)))^3*(1+4*x+x^2 +sqrt((1+4*x+x^2)^2 - 4*x*(1+x)*(3+2*x))) ) ).list()
    A119374_list(30) # G. C. Greubel, Mar 16 2021
    

Formula

G.f.: A(x) = B(x)^3/(1+x - x*B(x)) = B(x)^3*G(x) = B(x)^2*H(x) = B(x)*I(x), where B(x) is g.f. of A119370, G(x) is g.f. of A119371, H(x) is g.f. of A119372 and I(x) is g.f. of A119373.
G.f.: 16*(1+x)/( ((1+x^2) +sqrt((1+x^2)^2-4*x*(1+x)))^3*(1+4*x+x^2 +sqrt((1+4*x+x^2)^2 - 4*x*(1+x)*(3+2*x))) ).

A119375 Diagonal above the central terms of pendular trinomial triangle A119369, ignoring leading zeros.

Original entry on oeis.org

1, 3, 11, 40, 149, 564, 2166, 8420, 33074, 131085, 523599, 2105727, 8519469, 34652696, 141621164, 581266730, 2394961851, 9902433681, 41074316737, 170869972460, 712729001716, 2980264528670, 12490379959184, 52458339164169
Offset: 0

Views

Author

Paul D. Hanna, May 17 2006

Keywords

Crossrefs

Programs

  • Magma
    R:=PowerSeriesRing(Rationals(), 30);
    Coefficients(R!( (1-2*x-x^2 - Sqrt(1-4*x-2*x^2+x^4))/( 1+2*x^3+x^4 +(1+x)^2*Sqrt(1-4*x-2*x^2+x^4) ) )); // G. C. Greubel, Mar 16 2021
  • Mathematica
    CoefficientList[Series[(1-2*x-x^2 -Sqrt[1-4*x-2*x^2+x^4])/(x^2*(1+2*x^3+x^4 +(1+x)^2*Sqrt[1-4*x-2*x^2+x^4])), {x,0,30}], x] (* G. C. Greubel, Mar 16 2021 *)
  • PARI
    {a(n)=polcoeff(2/((1+x^2)+sqrt((1+x^2)^2-4*x*(1+x)+x^3*O(x^n)))* (2*(1+x)/(1+4*x+x^2 + sqrt((1+4*x+x^2)^2-4*x*(1+x)*(3+2*x)+x^3*O(x^n)))-1)/x^2,n)}
    
  • Sage
    def A119375_list(prec):
        P. = PowerSeriesRing(QQ, prec)
        return P( (1-2*x-x^2 -sqrt(1-4*x-2*x^2+x^4))/( x^2*(1+2*x^3+x^4 +(1+x)^2*sqrt(1-4*x-2*x^2+x^4)) ) ).list()
    A119375_list(30) # G. C. Greubel, Mar 16 2021
    

Formula

G.f.: A(x) = B(x)*(G(x) - 1)/x^2 = B(x)*(B(x) - 1)/(x+x^2 - x^2*B(x)), where B(x) is g.f. of A119370 and G(x) is g.f. of A119371 (central terms of A119369).
G.f.: (1-2*x-x^2 -sqrt(1-4*x-2*x^2+x^4))/( x^2*(1+2*x^3+x^4 +(1+x)^2*sqrt(1-4*x-2*x^2+x^4)) ). - G. C. Greubel, Mar 16 2021

A119376 Second diagonal above the central terms of pendular trinomial triangle A119369, ignoring leading zeros.

Original entry on oeis.org

1, 4, 16, 63, 248, 980, 3894, 15563, 62555, 252789, 1026623, 4188390, 17159382, 70570380, 291253664, 1205935204, 5008047097, 20854723702, 87064706122, 364334839028, 1527943938306, 6420911995109, 27033938458595
Offset: 0

Views

Author

Paul D. Hanna, May 17 2006

Keywords

Comments

Equals convolution of A119370 and A119375, which is the prior diagonal above the central terms of triangle A119369.

Crossrefs

Programs

  • Magma
    R:=PowerSeriesRing(Rationals(), 30);
    f:= func< x | Sqrt(1-4*x-2*x^2+x^4) >;
    Coefficients(R!( 2*(1-2*x-x^2 -f(x))/( x^2*(1+2*x^3+x^4 +(1+x)^2*f(x))*(1+x^2 +f(x)) ) )); // G. C. Greubel, Mar 17 2021
  • Mathematica
    f[x_]:= Sqrt[1-4*x-2*x^2+x^4];
    CoefficientList[Series[2*(1-2*x-x^2 -f[x])/(x^2*(1+2*x^3+x^4 +(1+x)^2*f[x])*(1+x^2 +f[x])), {x,0,30}], x] (* G. C. Greubel, Mar 17 2021 *)
  • PARI
    {a(n)=polcoeff(4/((1+x^2)+sqrt((1+x^2)^2-4*x*(1+x)+x^3*O(x^n)))^2* (2*(1+x)/(1+4*x+x^2 + sqrt((1+4*x+x^2)^2-4*x*(1+x)*(3+2*x)+x^3*O(x^n)))-1)/x^2,n)}
    
  • SageMath
    def f(x): return sqrt(1-4*x-2*x^2+x^4)
    def A119376_list(prec):
        P. = PowerSeriesRing(QQ, prec)
        return P( 2*(1-2*x-x^2 -f(x))/( x^2*(1+2*x^3+x^4 +(1+x)^2*f(x))*(1+x^2 +f(x)) ) ).list()
    A119376_list(30) # G. C. Greubel, Mar 17 2021
    

Formula

G.f.: A(x) = B(x)^2*(G(x) - 1)/x^2 = B(x)^2*(B(x) - 1)/(x+x^2 - x^2*B(x)), where B(x) is g.f. of A119370 and G(x) is g.f. of A119371 (central terms of A119369).
G.f.: 2*(1-2*x-x^2-f(x))/( x^2*(1+2*x^3+x^4+(1+x)^2*f(x))*(1+x^2+f(x)) ) where f(x) = sqrt(1-4*x-2*x^2+x^4). - G. C. Greubel, Mar 17 2021
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