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 1-4 of 4 results.

A071030 Triangle read by rows giving successive states of cellular automaton generated by "Rule 54".

Original entry on oeis.org

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

Views

Author

Hans Havermann, May 26 2002

Keywords

Comments

Row n has length 2n+1.
Even rows r sum to r/2 + 1, odd rows r sum to 3r to produce the sequence {1, 3, 2, 6, 3, 9, 4, 12, ...} = A064455(n + 1). - Michael De Vlieger, Oct 07 2015

Examples

			From _Michael De Vlieger_, Oct 07 2015: (Start)
First 12 rows, replacing "0" with "." for better visibility of ON cells:
                        1
                      1 1 1
                    1 . . . 1
                  1 1 1 . 1 1 1
                1 . . . 1 . . . 1
              1 1 1 . 1 1 1 . 1 1 1
            1 . . . 1 . . . 1 . . . 1
          1 1 1 . 1 1 1 . 1 1 1 . 1 1 1
        1 . . . 1 . . . 1 . . . 1 . . . 1
      1 1 1 . 1 1 1 . 1 1 1 . 1 1 1 . 1 1 1
    1 . . . 1 . . . 1 . . . 1 . . . 1 . . . 1
  1 1 1 . 1 1 1 . 1 1 1 . 1 1 1 . 1 1 1 . 1 1 1
1 . . . 1 . . . 1 . . . 1 . . . 1 . . . 1 . . . 1
(End)
		

References

  • S. Wolfram, A New Kind of Science, Wolfram Media, 2002; Chapter 3.

Crossrefs

Cf. A064455. See A118108 and A118109 for two other versions of this sequence.

Programs

  • Mathematica
    clip[lst_] := Block[{p = Flatten@ Position[lst, 1]}, Take[lst, {Min@ p, Max@ p}]]; clip /@ CellularAutomaton[54, {{1}, 0}, 8] // Flatten (* Michael De Vlieger, Oct 07 2015 *)

Extensions

Corrected by Hans Havermann, Jan 07 2012

A118108 Decimal representation of n-th iteration of the Rule 54 elementary cellular automaton starting with a single black cell.

Original entry on oeis.org

1, 7, 17, 119, 273, 1911, 4369, 30583, 69905, 489335, 1118481, 7829367, 17895697, 125269879, 286331153, 2004318071, 4581298449, 32069089143, 73300775185, 513105426295, 1172812402961, 8209686820727, 18764998447377, 131354989131639, 300239975158033
Offset: 0

Views

Author

Eric W. Weisstein, Apr 13 2006

Keywords

Comments

a(1660) is 1000 digits long. - Michael De Vlieger, Oct 07 2015

Examples

			From _Michael De Vlieger_, Oct 07 2015: (Start)
First 8 rows, representing ON cells as "1", OFF cells within the bounds of ON cells as "0", interpreted as a binary number at left, the decimal equivalent appearing at right:
                    1 =     1
                  111 =     7
               1 0001 =    17
             111 0111 =   119
          1 0001 0001 =   273
        111 0111 0111 =  1911
     1 0001 0001 0001 =  4369
   111 0111 0111 0111 = 30583
1 0001 0001 0001 0001 = 69905
(End)
		

Crossrefs

See A071030, A118109 for two other versions of this sequence.

Programs

  • Mathematica
    clip[lst_] := Block[{p = Flatten@ Position[lst, 1]}, Take[lst, {Min@ p, Max@ p}]]; FromDigits[#, 2] & /@ Map[clip, CellularAutomaton[54, {{1}, 0}, 27]] (* or *)
    Table[If[EvenQ@ n, (4^(n + 2) - 1), 7 (4^(n + 1) - 1)]/15, {n, 0, 27}] (* Michael De Vlieger, Oct 07 2015 *)
  • Python
    print([(16+12*(n%2))*4**n//15 for n in range(30)]) # Karl V. Keller, Jr., Aug 04 2021

Formula

a(n) = 7*(4^(n+1)-1)/15 for n odd; a(n) = (4^(n+2)-1)/15 for n even.
From Colin Barker, Oct 08 2015 and Apr 16 2019: (Start)
a(n) = 17*a(n-2) - 16*a(n-4) for n>3.
G.f.: (7*x+1) / ((x-1)*(x+1)*(4*x-1)*(4*x+1)).
(End)
a(n) = floor((16+12*(n mod 2))*4^n/15). - Karl V. Keller, Jr., Aug 04 2021

Extensions

a(23)-a(24) from Michael De Vlieger, Oct 07 2015

A265225 Total number of ON (black) cells after n iterations of the "Rule 54" elementary cellular automaton starting with a single ON (black) cell.

Original entry on oeis.org

1, 4, 6, 12, 15, 24, 28, 40, 45, 60, 66, 84, 91, 112, 120, 144, 153, 180, 190, 220, 231, 264, 276, 312, 325, 364, 378, 420, 435, 480, 496, 544, 561, 612, 630, 684, 703, 760, 780, 840, 861, 924, 946, 1012, 1035, 1104, 1128, 1200, 1225, 1300, 1326, 1404, 1431
Offset: 0

Views

Author

Robert Price, Dec 05 2015

Keywords

Comments

Take the first 2n positive integers and choose n of them such that their sum: a) is divisible by n, and b) is minimal. It seems their sum equals a(n). - Ivan N. Ianakiev, Feb 16 2019

Examples

			From _Michael De Vlieger_, Dec 14 2015: (Start)
First 12 rows, replacing "0" with "." for better visibility of ON cells, followed by the total number of 1's per row, and the running total up to that row:
                        1                          =  1 ->  1
                      1 1 1                        =  3 ->  4
                    1 . . . 1                      =  2 ->  6
                  1 1 1 . 1 1 1                    =  6 -> 12
                1 . . . 1 . . . 1                  =  3 -> 15
              1 1 1 . 1 1 1 . 1 1 1                =  9 -> 24
            1 . . . 1 . . . 1 . . . 1              =  4 -> 28
          1 1 1 . 1 1 1 . 1 1 1 . 1 1 1            = 12 -> 40
        1 . . . 1 . . . 1 . . . 1 . . . 1          =  5 -> 45
      1 1 1 . 1 1 1 . 1 1 1 . 1 1 1 . 1 1 1        = 15 -> 60
    1 . . . 1 . . . 1 . . . 1 . . . 1 . . . 1      =  6 -> 66
  1 1 1 . 1 1 1 . 1 1 1 . 1 1 1 . 1 1 1 . 1 1 1    = 18 -> 84
1 . . . 1 . . . 1 . . . 1 . . . 1 . . . 1 . . . 1  =  7 -> 91
(End)
		

References

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

Crossrefs

Programs

  • Maple
    A265225:=n->1/4*(n+1)*(2*n-(-1)^n+5): seq(A265225(n), n=0..60); # Wesley Ivan Hurt, Dec 25 2016
  • Mathematica
    rule = 54; rows = 30; Table[Total[Take[Table[Total[Table[Take[CellularAutomaton[rule,{{1},0},rows-1,{All,All}][[k]],{rows-k+1,rows+k-1}],{k,1,rows}][[k]]],{k,1,rows}],k]],{k,1,rows}]
    Accumulate[Total /@ CellularAutomaton[54, {{1}, 0}, 52]]

Formula

Conjectures from Colin Barker, Dec 08 2015 and Apr 20 2019: (Start)
a(n) = (n+1)*(2*n -(-1)^n +5)/4.
a(n) = a(n-1) + 2*a(n-2) - 2*a(n-3) - a(n-4) + a(n-5) for n>4.
G.f.: (1+3*x) / ((1-x)^3*(1+x)^2).
(End)
a(n) = n + 1 + (n+1) * floor((n+1)/2), conjectured. - Wesley Ivan Hurt, Dec 25 2016
a(n) = A093353(n) + n + 1, conjectured. - Matej Veselovac, Jan 21 2020

A259661 Binary representation of the middle column of the "Rule 54" elementary cellular automaton starting with a single ON (black) cell.

Original entry on oeis.org

1, 11, 110, 1100, 11001, 110011, 1100110, 11001100, 110011001, 1100110011, 11001100110, 110011001100, 1100110011001, 11001100110011, 110011001100110, 1100110011001100, 11001100110011001, 110011001100110011, 1100110011001100110, 11001100110011001100
Offset: 0

Views

Author

Robert Price, Dec 05 2015

Keywords

Examples

			From _Michael De Vlieger_, Dec 09 2015: (Start)
First 8 rows at left, ignoring "0" outside of range of 1's, the center column values in parentheses, and at right the value of center column cells up to that row:
                (1)                 -> 1
              1 (1) 1               -> 11
            1 0 (0) 0 1             -> 110
          1 1 1 (0) 1 1 1           -> 1100
        1 0 0 0 (1) 0 0 0 1         -> 11001
      1 1 1 0 1 (1) 1 0 1 1 1       -> 110011
    1 0 0 0 1 0 (0) 0 1 0 0 0 1     -> 1100110
  1 1 1 0 1 1 1 (0) 1 1 1 0 1 1 1   -> 11001100
1 0 0 0 1 0 0 0 (1) 0 0 0 1 0 0 0 1 -> 110011001
(End)
		

Crossrefs

Programs

  • Mathematica
    lim = 20; Take[Last@ Take[#, Ceiling[Length[#]/2]] & /@ CellularAutomaton[54, {{1}, 0}, lim], #] & /@ Range@ lim (* Michael De Vlieger, Dec 09 2015 *)

Formula

Conjectures from Colin Barker, Dec 08 2015 and Apr 17 2019: (Start)
a(n) = 11*a(n-1) - 11*a(n-2) + 11*a(n-3) - 10*a(n-4) for n>3.
G.f.: 1 / ((1-x)*(1-10*x)*(1+x^2)).
(End)
Showing 1-4 of 4 results.