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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A106688 Six-symbol substitution: characteristic polynomial: x^6 - 4*x^4 - 3*x^3 - x - 1.

Original entry on oeis.org

2, 4, 2, 5, 6, 3, 4, 3, 6, 1, 4, 5, 2, 4, 2, 5, 6, 2, 4, 1, 4, 5, 2, 2, 5, 6, 3, 6, 3, 4, 2, 5, 6, 3, 4, 3, 6, 1, 4, 5, 3, 4, 2, 5, 6, 2, 2, 5, 6, 3, 6, 3, 4, 3, 4, 3, 6, 1, 4, 5, 2, 4, 1, 4, 5, 2, 4, 2, 5, 6, 3, 4, 3, 6, 1, 4, 5, 2, 4, 2, 5, 6, 2, 4, 1, 4, 5, 2, 2, 5, 6, 3, 6, 2, 4, 2, 5, 6, 3, 4, 3, 6, 1, 4, 5
Offset: 0

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Author

Roger L. Bagula, May 13 2005

Keywords

Examples

			[1] -> [2] -> [3,4] -> [2,4,2,5,6] -> [3,4,2,5,6,3,4,3,6,1,4,5] -> ... Lengths of iterates is 1,1,2,5,12,28,... = A034943. - _Michael Somos_
		

Programs

  • Mathematica
    s[1] = {2}; s[2] = {3, 4}; s[3] = {2, 4}; s[4] = {2, 5, 6}; s[5] = {3, 6}; s[6] = {1, 4, 5}; t[a_] := Flatten[s /@ a]; p[0] = {1}; p[1] = t[p[0]]; p[n_] := t[p[n - 1]] aa = p[7]
  • PARI
    {a(n)=my(A); if(n<1,0, A=[2]; while(length(A)Michael Somos, May 16 2005 */

Formula

1->{2}, 2->{3, 4}, 3->{2, 4}, 4->{2, 5, 6}, 5->{3, 6}, 6->{1, 4, 5}

A216344 Triangle T(n,k), read by rows, given by (0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, ...) DELTA (1, 0, 0, -1, 1, 0, 0, 0, 0, 0, ...) where DELTA is the operator defined in A084938 .

Original entry on oeis.org

1, 0, 1, 0, 1, 1, 0, 2, 2, 1, 0, 4, 4, 3, 1, 0, 8, 8, 7, 4, 1, 0, 16, 16, 16, 11, 5, 1, 0, 32, 32, 36, 28, 16, 6, 1, 0, 64, 64, 80, 68, 45, 22, 7, 1, 0, 128, 128, 176, 160, 118, 68, 29, 8, 1, 0, 256, 256, 384
Offset: 0

Views

Author

Philippe Deléham, Sep 04 2012

Keywords

Examples

			Triangle begins :
1
0, 1
0, 1, 1
0, 2, 2, 1
0, 4, 4, 3, 1
0, 8, 8, 7, 4, 1
0, 16, 16, 16, 11, 5, 1
0, 32, 32, 36, 28, 16, 6, 1
		

Crossrefs

Formula

G.f.: (1-2*x+y*x^2)/(1-2*x-y*x+2*y*x^2-y^2*x^3)
T(n,k) = 2*T(n-1,k) + T(n-1,k-1) - 2*T(n-2,k-1) + T(n-3,k-2), T(0,0) = T(1,1) = T(2,1) = T(2,2) = 1, T(1,0) = T(2,0) = 0 and T(n,k) = 0 if k<0 or if k>n .
Sum_{k, 0<=k<=n} T(n,k) = A034943(n+1) .
Sum_{k, 0<=k<=n} T(n,k)*2^k*(-1/2)^(n-k) = A052955(n) .
T(n+1,1) = A011782(n), T(n+2,2) = 2^n = A000079(n), T(n+3,3) = A045891(n+1) .
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