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 1-6 of 6 results.

A118111 Binary representation of n-th iteration of the Rule 190 elementary cellular automaton starting with a single black cell.

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 0, 1
Offset: 0

Views

Author

Eric W. Weisstein, Apr 13 2006

Keywords

Comments

Row n has length 2*n+1. - Hans Havermann, May 26 2002

Examples

			From _Michael De Vlieger_, Aug 21 2020: (Start)
Irregular array begins:
0:                             1
1:                          1  1  1
2:                       1  1  1  0  1
3:                    1  1  1  0  1  1  1
4:                 1  1  1  0  1  1  1  0  1
5:              1  1  1  0  1  1  1  0  1  1  1
6:           1  1  1  0  1  1  1  0  1  1  1  0  1
7:        1  1  1  0  1  1  1  0  1  1  1  0  1  1  1
8:     1  1  1  0  1  1  1  0  1  1  1  0  1  1  1  0  1
9:  1  1  1  0  1  1  1  0  1  1  1  0  1  1  1  0  1  1  1
... (End)
		

Crossrefs

Cf. A265688 (binary rows), A037576 (decimal rows), A032766 (num 1's).

Programs

  • Mathematica
    With[{nn = 9}, MapIndexed[#1[[#2 + 1 ;; 2 nn - #2 + 1]] & @@ {#1, nn - First[#2] + 1} &, CellularAutomaton[190, {{1}, 0}, nn]]] // Flatten (* Michael De Vlieger, Aug 21 2020 *)

A265688 Binary representation of the n-th iteration of the "Rule 190" elementary cellular automaton starting with a single ON (black) cell.

Original entry on oeis.org

1, 111, 11101, 1110111, 111011101, 11101110111, 1110111011101, 111011101110111, 11101110111011101, 1110111011101110111, 111011101110111011101, 11101110111011101110111, 1110111011101110111011101, 111011101110111011101110111, 11101110111011101110111011101
Offset: 0

Views

Author

Robert Price, Dec 13 2015

Keywords

References

  • S. Wolfram, A New Kind of Science, Wolfram Media, 2002; p. 55.

Crossrefs

Cf. A037576 (decimal), A118111.

Programs

  • Mathematica
    rule = 190; rows = 20; Table[FromDigits[Table[Take[CellularAutomaton[rule,{{1},0}, rows-1, {All,All}][[k]], {rows-k+1, rows+k-1}], {k,1,rows}][[k]]], {k,1,rows}]
  • Python
    print([11100*100**n//9999 for n in range(30)]) # Karl V. Keller, Jr., Aug 10 2021

Formula

From Colin Barker, Dec 13 2015 and Apr 18 2019: (Start)
a(n) = (-165*(-1)^n+37*100^(n+1)-202)/3333.
a(n) = (37*100^(n+1)-367)/3333 for n even.
a(n) = (37*100^(n+1)-37)/3333 for n odd.
a(n) = 100*a(n-1) + a(n-2) - 100*a(n-3) for n>2.
G.f.: (1+11*x) / ((1-x)*(1+x)*(1-100*x)).
(End)
a(n) = floor(11100*100^n/9999). - Karl V. Keller, Jr., Aug 10 2021

A028894 a(n) = either 4a(n-1)+1 or 4a(n-1)+3 depending on corresponding term of A005614, +1 for 0, +3 for 1.

Original entry on oeis.org

1, 5, 23, 95, 381, 1527, 6109, 24439, 97759, 391037, 1564151, 6256607, 25026429, 100105719, 400422877, 1601691511, 6406766047, 25627064189, 102508256759, 410033027037, 1640132108151, 6560528432607, 26242113730429
Offset: 1

Views

Author

John McNamara, Jan 12 2002

Keywords

Crossrefs

Programs

  • Mathematica
    f[1]={0}; f[2]={1}; f[n_] := f[n]=Join[f[n-1], f[n-2]]; a[1]=1; a[n_] := a[n]=4a[n-1]+1+2f[9][[n]]; a/@Range[1, 30]

Extensions

Edited by Dean Hickerson, Jan 14 2002

A066744 a(n) = either 4a(n-1)+1 or 4a(n-1)+3 depending on corresponding term of A005614, +3 for 0, +1 for 1.

Original entry on oeis.org

1, 7, 29, 117, 471, 1885, 7543, 30173, 120693, 482775, 1931101, 7724405, 30897623, 123590493, 494361975, 1977447901, 7909791605, 31639166423, 126556665693, 506226662775, 2024906651101, 8099626604405, 32398506417623
Offset: 1

Views

Author

John McNamara, Jan 16 2002

Keywords

Comments

Ratio to terms of A028894 tends to 1.23459972586...

Crossrefs

Programs

  • Mathematica
    f[1]={0}; f[2]={1}; f[n_] := f[n]=Join[f[n-1], f[n-2]]; a[1]=1; a[n_] := a[n]=4a[n-1]+3-2f[9][[n]]; a/@Range[1, 30]

A102865 Base-4 digits are, in order, the first n terms of the sequence (1, 3, 21, 203, 2021, 20203, 202021, 2020203, 20202021, 202020203, ... ).

Original entry on oeis.org

1, 3, 9, 35, 137, 547, 2185, 8739, 34953, 139811, 559241, 2236963, 8947849, 35791395, 143165577, 572662307, 2290649225, 9162596899, 36650387593, 146601550371, 586406201481, 2345624805923, 9382499223689, 37529996894755, 150119987579017, 600479950316067
Offset: 0

Views

Author

Creighton Dement, Mar 01 2005

Keywords

Crossrefs

Cf. A037576.

Programs

  • Mathematica
    FromDigits[IntegerDigits[#],4]&/@(NestList[FromDigits[Flatten[ IntegerDigits[#]/.{3->{2,1},1->{0,3}}]]&,1,30]) (* or *) LinearRecurrence[{4,1,-4},{1,3,9},31](* Harvey P. Dale, Mar 23 2012 *)

Formula

4^n = a(n) + A037576(n) for n >= 1.
a(n) + a(n+1) = A039301(n+2).
a(n) = 4*a(n-1) + a(n-2) - 4*a(n-3). - Harvey P. Dale, Mar 23 2012
G.f.: 1 + x*(3-3*x-4*x^2)/((1-x)*(1+x)*(1-4*x)). - Colin Barker, Aug 28 2012

Extensions

More terms from Harvey P. Dale, Mar 23 2012

A140320 a(n) = A137576((3^n-1)/2).

Original entry on oeis.org

1, 3, 13, 55, 217, 811, 2917, 10207, 34993, 118099, 393661, 1299079, 4251529, 13817467, 44641045, 143489071, 459165025, 1463588515, 4649045869, 14721978583, 46490458681, 146444944843, 460255540933, 1443528742015, 4518872583697, 14121476824051, 44059007691037, 137260754729767
Offset: 0

Views

Author

Vladimir Shevelev, May 26 2008

Keywords

Comments

Conjecture. a(n) = 2n*3^(n-1)+1.
If conjecture is true then limsup(A137576(n)/n)=infinity while liminf(A137576(n)/n)=2 with a realization on primes.
a(n) is also the number of edges in the graph generated from the n-dimensional hypercube (plus 1) in the following manner: connect all (d + 1)-dimensional faces to the d faces that are incident. Each d-dimensional face should be incident on (n - d) (d + 1)-dimensional faces. [Roy Liu (royliu(AT)cs.ucsd.edu), Jul 26 2010]

Crossrefs

Programs

  • PARI
    a137576(n) = my(t); sumdiv(2*n+1, d, eulerphi(d)/(t=znorder(Mod(2, d))))*t-t+1;
    a(n) = a137576((3^n-1)/2); \\ Michel Marcus, Dec 18 2018

Formula

Sum_{m = 0}^{n} 2^(n - m) * binomial(n,m) is the number of m-dimensional faces in the n-dimensional hypercube. Consequently, Sum_{m = 0..n} (n - m) * 2^(n - m) * binomial(n,m) gives the number of incidence edges, which yields said sequence minus 1. The recurrence relation is: a(n) = 3 * a(n - 1) + 2 * 3^(n - 1) - 2. [Roy Liu (royliu(AT)cs.ucsd.edu), Jul 26 2010]
Empirical G.f.: (1-4*x+7*x^2)/(1-7*x+15*x^2-9*x^3). [Colin Barker, Jan 09 2012]

Extensions

More terms from Michel Marcus, Dec 18 2018
Showing 1-6 of 6 results.