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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A118438 Triangle T, read by rows, equal to the matrix product T = H*C*H, where H is the self-inverse triangle A118433 and C is Pascal's triangle.

Original entry on oeis.org

1, -1, 1, 5, -2, 1, 11, -9, -3, 1, -23, 44, 30, -4, 1, -41, 125, 110, -30, -5, 1, 45, -246, -345, 220, 75, -6, 1, -29, -301, -861, 875, 385, -63, -7, 1, 337, -232, 1260, -2296, -1610, 616, 140, -8, 1, 1199, -3015, -1044, -3612, -5166, 3150, 924, -108, -9, 1
Offset: 0

Views

Author

Paul D. Hanna, Apr 28 2006

Keywords

Comments

The matrix inverse of H*C*H is H*[C^-1]*H = A118435, where H^2 = I (identity). The matrix log, log(T) = -A118441, is a matrix square root of a triangular matrix with a single diagonal (two rows down from the main diagonal).

Examples

			Triangle begins:
1;
-1, 1;
5,-2, 1;
11,-9,-3, 1;
-23, 44, 30,-4, 1;
-41, 125, 110,-30,-5, 1;
45,-246,-345, 220, 75,-6, 1;
-29,-301,-861, 875, 385,-63,-7, 1;
337,-232, 1260,-2296,-1610, 616, 140,-8, 1;
1199,-3015,-1044,-3612,-5166, 3150, 924,-108,-9, 1; ...

Crossrefs

Cf. A118439 (column 0), A118440 (row sums), A118435 (matrix inverse), A118441 (-matrix log); A118433 (self-inverse H).

Programs

  • Mathematica
    nmax = 12;
h[n_, k_] := Binomial[n, k]*(-1)^(Quotient[n+1, 2] - Quotient[k, 2]+n-k);
H = Table[h[n, k], {n, 0, nmax}, {k, 0, nmax}];
Cn = Table[Binomial[n, k], {n, 0, nmax}, {k, 0, nmax}];
Tn = H.Cn.H;
T[n_, k_] := Tn[[n+1, k+1]];
Table[T[n, k], {n, 0, nmax}, {k, 0, n}] // Flatten (* Jean-François Alcover, Apr 08 2024 *)
  • PARI
    {T(n,k)=local(M=matrix(n+1,n+1,r,c,if(r>=c,binomial(r-1,c-1)*(-1)^(r\2- (c-1)\2+r-c))),C=matrix(n+1,n+1,r,c,if(r>=c,binomial(r-1,c-1))));(M*C*M)[n+1,k+1]}

Formula

Since T + T^-1 = C + C^-1, then [T^-1](n,k) = (1+(-1)^(n-k))*C(n,k) - T(n,k) is a formula for the matrix inverse T^-1 = A118435.

A118440 Row sums of triangle A118438.

Original entry on oeis.org

1, 0, 4, 0, 48, 160, -256, 0, -1792, -7680, 16384, 0, 135168, 532480, -1048576, 0, -8323072, -33423360, 67108864, 0, 537919488, 2149580800, -4294967296, 0, -34342961152, -137405399040, 274877906944, 0, 2199291691008, 8796629893120, -17592186044416, 0, -140733193388032, -562941363486720
Offset: 0

Views

Author

Paul D. Hanna, Apr 28 2006

Keywords

Links

Crossrefs

Cf. A118438 (triangle), A118439 (column 0); A118437 (row sums of inverse).

Programs

  • Mathematica
    CoefficientList[Series[(1-2x+8x^2-16x^3+128x^4-96x^5+128x^6-256x^7)/ (1-2x)/(1+4x^2)/(1+64x^4),{x,0,50}],x] (* or *) Join[{1}, LinearRecurrence[ {2,-4,8,-64,128,-256,512},{0,4,0,48,160,-256,0},50]]  (* Harvey P. Dale, Apr 30 2011 *)
  • PARI
    {a(n)=polcoeff((1-2*x+8*x^2-16*x^3+128*x^4-96*x^5+128*x^6-256*x^7)/(1-2*x)/(1+4*x^2)/(1+64*x^4+x*O(x^n)),n)}

Formula

G.f.: (1-2*x+8*x^2-16*x^3+128*x^4-96*x^5+128*x^6-256*x^7)/(1-2*x)/(1+4*x^2)/(1+64*x^4).
Showing 1-2 of 2 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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