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.

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A134410 Second-order Lucas numbers; a(n) = (2n+3)*Lucas(n) - n*Lucas(n-1).

Original entry on oeis.org

6, 3, 19, 27, 61, 108, 204, 367, 661, 1173, 2069, 3622, 6306, 10923, 18839, 32367, 55421, 94608, 161064, 273527, 463481, 783753, 1322869, 2229002, 3749886, 6299283, 10567579, 17705667, 29630461, 49532148, 82715844, 137997247, 230015581, 383064573, 637434389
Offset: 0

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Author

Peter Bala, Oct 24 2007

Keywords

Comments

This sequence is defined by analogy with the sequence of second-order Fibonacci numbers A010049.
Inverse binomial transform is (-1)^n * a(n). - Michael Somos, Jun 02 2014

Examples

			G.f. = 6 + 3*x + 19*x^2 + 27*x^3 + 61*x^4 + 108*x^5 + 204*x^6 + 367*x^7 + ...
		

Crossrefs

Programs

  • Mathematica
    a[ n_] := 3 (n + 1) LucasL[n] - n LucasL[n + 1]; (* Michael Somos, Jun 02 2014 *)
    LinearRecurrence[{2,1,-2,-1},{6,3,19,27},40] (* Harvey P. Dale, Jun 26 2017 *)
  • PARI
    {a(n) = (6 + 5*n) * fibonacci(n+1) - (3 + 5*n) * fibonacci(n)}; /* Michael Somos, Jun 02 2014 */
    
  • PARI
    Vec((2-x)*(3-3*x+2*x^2)/(1-x-x^2)^2 + O(x^40)) \\ Colin Barker, Jun 02 2016

Formula

Defining equation: a(n) = (2n+3)*Lucas(n) - n*Lucas(n-1).
Recurrence: a(0) = 6, a(1) = 3, a(n+2) = a(n+1) + a(n) + 5*Lucas(n).
O.g.f.: (2-x)*(3-3x+2x^2)/(1-x-x^2)^2.
Set A(n) = (a(n-1) + a(n+1))/5, B(n) = a(n+1) - a(n-1). Then A(n+2) = A(n+1) + A(n) + 5*Fibonacci(n) and B(n+2) = B(n+1) + B(n) + 5*Lucas(n). The polynomials L_2(n,-x) = sum {k = 0..n} C(n,k)*a(n-k)*(-x)^k appear to satisfy a Riemann hypothesis; their zeros appear to lie on the vertical line Re x = 1/2 in the complex plane. Compare with the polynomials L(n,-x) defined in A132148.
0 = a(n)*(-a(n) - 4*a(n+1) + a(n+2)) + a(n+1)*(-3*a(n+1) + 6*a(n+2) - a(n+3)) + a(n+2)*(+3*a(n+2) - 4*a(n+3)) + a(n+3)*(+a(n+3)) for all n in Z. - Michael Somos, Jun 02 2014
a(n) = 2^(-1-n)*(6*((1-sqrt(5))^n+(1+sqrt(5))^n)+(-(-5+sqrt(5))*(1+sqrt(5))^n+(1-sqrt(5))^n*(5+sqrt(5)))*n). - Colin Barker, Jun 02 2016

A136531 Coefficients of polynomials B(x,n) = ((1+a+b)*x - c)*B(x,n-1) - a*b*B(x,n-2) where B(x,0) = 1, B(x,1) = x, a=-b, b=1, c=1.

Original entry on oeis.org

1, 0, 1, 1, -1, 1, -1, 3, -2, 1, 2, -5, 6, -3, 1, -3, 10, -13, 10, -4, 1, 5, -18, 29, -26, 15, -5, 1, -8, 33, -60, 65, -45, 21, -6, 1, 13, -59, 122, -151, 125, -71, 28, -7, 1, -21, 105, -241, 338, -321, 217, -105, 36, -8, 1, 34, -185, 468, -730, 784, -609, 350, -148, 45, -9, 1
Offset: 0

Views

Author

Roger L. Bagula, Mar 23 2008

Keywords

Examples

			Triangle begins
        k=0  k=1  k=2  k=3  k=4  k=5  k=6
  n=0:   1;
  n=1:   0,   1;
  n=2:   1,  -1,   1;
  n=3:  -1,   3,  -2,   1;
  n=4:   2,  -5,   6,  -3,   1;
  n=5:  -3,  10, -13,  10,  -4,   1;
  n=6:   5, -18,  29, -26,  15,  -5,   1;
		

Crossrefs

Programs

  • Magma
    C := ComplexField(); // T = A136531
    T:= func< n,k | k eq n select 1 else Round(i^(k-n-1)*(i*Evaluate(GegenbauerPolynomial(n-k, k+1), 1/(2*i)) - Evaluate(GegenbauerPolynomial(n-k-1, k+1), 1/(2*i)))) >;
    [T(n,k): k in [0..n], n in [0..12]]; // G. C. Greubel, Sep 26 2022
    
  • Mathematica
    (* First program *)
    a = -b; c = 1; b = 1;
    B[x_, n_]:= B[x, n]= If[n<2, x^n, ((1+a+b)*x -c)*B[x, n-1] -a*b*B[x, n-2]];
    Table[CoefficientList[B[x,n], x], {n,0,10}]//Flatten
    (* Second program *)
    B[x_, n_]:= (-1)^n*(Fibonacci[n+1, 1-x] - Fibonacci[n, 1-x]);
    Table[CoefficientList[B[x, n], x], {n,0,16}]//Flatten (* G. C. Greubel, Sep 22 2022 *)
  • SageMath
    def T(n,k): # T = A136531
        if k==n: return 1
        else: return i^(k-n-1)*(i*gegenbauer(n-k, k+1, 1/(2*i)) - gegenbauer(n-k-1, k+1, 1/(2*i)))
    flatten([[T(n,k) for k in range(n+1)] for n in range(12)]) # G. C. Greubel, Sep 26 2022

Formula

G.f.: (1+y) / (1 + (1-x)*y - y^2). - Kevin Ryde, Sep 21 2022
From G. C. Greubel, Sep 22 2022: (Start)
T(n, k) = coefficients of i^n*(ChebyshevU(n, (x-1)/(2*i)) - i*ChebyshevU(n-1, (x-1)/(2*i))).
T(n, k) = coefficients of (-1)^n*( Fibonacci(n+1, 1-x) - Fibonacci(n, 1-x) ).
T(n, k) = i^(k-n-1)*(i*GegenbauerC(n-k, k+1, 1/(2*i)) - GegenbauerC(n-k-1, k+1, 1/(2*i))).
T(n, 0) = Fibonacci(1-n) = (-1)^n*A212804(n) = A039834(n-1).
T(n, 1) = (-1)^(n-1)*A010049(n), n >= 1.
T(n, 2) = (-1)^n*A055243(n-2), n >= 2.
T(n, n) = 1.
T(n, n-1) = -(n-1).
T(n, n-2) = A000217(n-1), n >= 2.
T(n, n-3) = -A008728(n-3), n >= 3.
Sum_{k=0..n-2} T(n, k) = A000027(n-1), n >= 2.
Sum_{k=0..n} T(n, k) = 1.
Sum_{k=0..floor(n/2)} T(n-k, k) = A151575(n) = (-1)^n*A078008(n). (End)

Extensions

Offset corrected by Kevin Ryde, Sep 21 2022

A135830 A000012(signed) * A049310 * A000012.

Original entry on oeis.org

1, 0, 1, 2, 0, 1, 1, 3, 0, 1, 4, 1, 4, 0, 1, 4, 7, 1, 5, 0, 1, 9, 5, 11, 1, 6, 0, 1, 12, 16, 6, 16, 1, 7, 0, 1, 22, 17, 27, 7, 22, 1, 8, 0, 1, 33, 38, 23, 43, 8, 29, 1, 9, 0, 1
Offset: 1

Author

Gary W. Adamson, Nov 30 2007

Keywords

Comments

Row sums A010049: (1, 1, 3, 5, 10, 18, 33, ...).

Examples

			First few rows of the triangle:
   1;
   0,  1;
   2,  0,  1;
   1,  3,  0,  1;
   4,  1,  4,  0,  1;
   4,  7,  1,  5,  0,  1;
   9,  5, 11,  1,  6,  0,  1;
  12, 16,  6, 16,  1,  7,  0,  1;
  ...
		

Crossrefs

Formula

A000012(signed) * A049310 * A000012, as infinite lower triangular matrices, where A000012(signed) = (1; -1,1; 1,-1,1; ...).

A239366 Triangular array read by rows: T(n,k) is the number of palindromic compositions of n having exactly k 1's, n>=0, 0<=k<=n.

Original entry on oeis.org

1, 0, 1, 1, 0, 1, 1, 0, 0, 1, 2, 0, 1, 0, 1, 1, 1, 1, 0, 0, 1, 3, 0, 3, 0, 1, 0, 1, 2, 1, 1, 2, 1, 0, 0, 1, 5, 0, 5, 0, 4, 0, 1, 0, 1, 3, 2, 3, 2, 1, 3, 1, 0, 0, 1, 8, 0, 10, 0, 7, 0, 5, 0, 1, 0, 1, 5, 3, 5, 5, 4, 3, 1, 4, 1, 0, 0, 1, 13, 0, 18, 0, 16, 0, 9, 0, 6, 0, 1, 0, 1, 8, 5, 10, 8, 7, 9, 5, 4, 1, 5, 1, 0, 0, 1
Offset: 0

Author

Geoffrey Critzer, Mar 20 2014

Keywords

Comments

Row sums = 2^floor(n/2).
T(n,0) = A053602(n-1) for n>0, T(n,1) = A079977(n-5) for n>4, T(2n+1,3) = A006367(n-1) for n>0, both bisections of column k=2 contain A010049. - Alois P. Heinz, Mar 21 2014

Examples

			1,
0, 1,
1, 0, 1,
1, 0, 0, 1,
2, 0, 1, 0, 1,
1, 1, 1, 0, 0, 1,
3, 0, 3, 0, 1, 0, 1,
2, 1, 1, 2, 1, 0, 0, 1,
5, 0, 5, 0, 4, 0, 1, 0, 1,
3, 2, 3, 2, 1, 3, 1, 0, 0, 1
There are eight palindromic compositions of 6: T(6,0)=3 because we have: 6, 3+3, 2+2+2.  T(6,2)=3 because we have: 1+4+1, 2+1+1+2, 1+2+2+1.  T(6,4)=1 because we have: 1+1+2+1+1. T(6,6)=1 because we have: 1+1+1+1+1+1.
		

Programs

  • Maple
    b:= proc(n) option remember;  `if`(n=0, 1, expand(
          add(b(n-j)*`if`(j=1, x^2, 1), j=1..n)))
        end:
    T:= n-> (p-> seq(coeff(p, x, i), i=0..n))
        (add(b(i)*`if`(n-2*i=1, x, 1), i=0..n/2)):
    seq(T(n), n=0..30);  # Alois P. Heinz, Mar 21 2014
  • Mathematica
    nn=15;Table[Take[CoefficientList[Series[((1+x)*(1-x+x^2+x*y-x^2*y))/(1-x^2-x^4-x^2*y^2+x^4*y^2),{x,0,nn}],{x,y}][[n]],n],{n,1,nn}]//Grid

Formula

G.f.: G(x,y) = ((1 + x)*(1 - x + x^2 + x*y - x^2*y))/(1 - x^2 - x^4 - x^2*y^2 + x^4*y^2). Satisfies G(x,y) = 1/(1 - x) - x + y*x + (x^2/(1 - x^2) - x^2 +y^2*x^2)*G(x,y).
Previous Showing 21-24 of 24 results.