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 1-10 of 12 results. Next

A267610 Total number of OFF (white) cells after n iterations of the "Rule 182" elementary cellular automaton starting with a single ON (black) cell.

Original entry on oeis.org

0, 0, 2, 2, 4, 6, 12, 12, 14, 16, 22, 24, 30, 36, 50, 50, 52, 54, 60, 62, 68, 74, 88, 90, 96, 102, 116, 122, 136, 150, 180, 180, 182, 184, 190, 192, 198, 204, 218, 220, 226, 232, 246, 252, 266, 280, 310, 312, 318, 324, 338, 344, 358, 372, 402, 408, 422, 436
Offset: 0

Views

Author

Robert Price, Jan 18 2016

Keywords

Comments

From Gus Wiseman, Mar 30 2019: (Start)
It appears that a(n) is also the number of increasing binary-containment pairs of distinct positive integers up to n + 1. A pair of positive integers is a binary containment if the positions of 1's in the reversed binary expansion of the first are a subset of the positions of 1's in the reversed binary expansion of the second. For example, the a(2) = 2 through a(8) = 14 pairs are:
{1,3} {1,3} {1,3} {1,3} {1,3} {1,3} {1,3}
{2,3} {2,3} {1,5} {1,5} {1,5} {1,5} {1,5}
{2,3} {2,3} {1,7} {1,7} {1,7}
{4,5} {2,6} {2,3} {2,3} {1,9}
{4,5} {2,6} {2,6} {2,3}
{4,6} {2,7} {2,7} {2,6}
{3,7} {3,7} {2,7}
{4,5} {4,5} {3,7}
{4,6} {4,6} {4,5}
{4,7} {4,7} {4,6}
{5,7} {5,7} {4,7}
{6,7} {6,7} {5,7}
{6,7}
{8,9}
(End)

References

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

Crossrefs

Programs

  • Mathematica
    rule=182; rows=20; ca=CellularAutomaton[rule,{{1},0},rows-1,{All,All}]; (* Start with single black cell *) catri=Table[Take[ca[[k]],{rows-k+1,rows+k-1}],{k,1,rows}]; (* Truncated list of each row *) nbc=Table[Total[catri[[k]]],{k,1,rows}]; (* Number of Black cells in stage n *) nwc=Table[Length[catri[[k]]]-nbc[[k]],{k,1,rows}]; (* Number of White cells in stage n *) Table[Total[Take[nwc,k]],{k,1,rows}] (* Number of White cells through stage n *)

Formula

Conjecture: a(n) = A267700(n) - n. - Gus Wiseman, Mar 30 2019
G.f.: (1/x)*(A(x)/x - (x+1)/(1-x)^2) where A(x) is the g.f. for A006046 (conjectured). - John Tyler Rascoe, Jul 08 2024

A267700 "Tree" sequence in a 90-degree sector of the cellular automaton of A160720.

Original entry on oeis.org

0, 1, 2, 5, 6, 9, 12, 19, 20, 23, 26, 33, 36, 43, 50, 65, 66, 69, 72, 79, 82, 89, 96, 111, 114, 121, 128, 143, 150, 165, 180, 211, 212, 215, 218, 225, 228, 235, 242, 257, 260, 267, 274, 289, 296, 311, 326, 357, 360, 367, 374, 389, 396, 411, 426, 457, 464, 479, 494, 525, 540, 571, 602, 665, 666, 669, 672, 679, 682, 689
Offset: 0

Views

Author

Omar E. Pol, Jan 19 2016

Keywords

Comments

Conjecture: this is also the "tree" sequence in a 120-degree sector of the cellular automaton of A266532.
It appears that this is also the partial sums of A038573.
a(n) is also the total number of ON cells after n-th stage in the tree that arises from one of the four spokes in a 90-degree sector of the cellular automaton A160720 on the square grid.
Note that the structure of A160720 is also the "outward" version of the Ulam-Warburton cellular automaton of A147562.
It appears that A038573 gives the number of cells turned ON at n-th stage.
Conjecture: a(n) is also the total number of Y-toothpicks after n-th stage in the tree that arises from one of the three spokes in a 120-degree sector of the cellular automaton of A266532 on the triangular grid.
Note that the structure of A266532 is also the "outward" version of the Y-toothpick cellular automaton of A160120.
It appears that A038573 also gives the number of Y-toothpicks added at n-th stage.
Comment from N. J. A. Sloane, Jan 23 2016: All the above conjectures are true!
From Gus Wiseman, Mar 31 2019: (Start)
a(n) is also the number of nondecreasing binary-containment pairs of positive integers up to n. A pair of positive integers is a binary containment if the positions of 1's in the reversed binary expansion of the first are a subset of the positions of 1's in the reversed binary expansion of the second. For example, the a(1) = 1 through a(6) = 12 pairs are:
(1,1) (1,1) (1,1) (1,1) (1,1) (1,1)
(2,2) (1,3) (1,3) (1,3) (1,3)
(2,2) (2,2) (1,5) (1,5)
(2,3) (2,3) (2,2) (2,2)
(3,3) (3,3) (2,3) (2,3)
(4,4) (3,3) (2,6)
(4,4) (3,3)
(4,5) (4,4)
(5,5) (4,5)
(4,6)
(5,5)
(6,6)
(End)

Crossrefs

Programs

  • Mathematica
    Accumulate[Table[2^DigitCount[n,2,1]-1,{n,0,30}]] (* based on conjecture confirmed by Sloane, Gus Wiseman, Mar 31 2019 *)

Formula

a(n) = (A160720(n+1) - 1)/4.
Conjecture 1: a(n) = (A266532(n+1) - 1)/3.
Conjecture 2: a(n) = A160720(n+1) - A266532(n+1).
All of the above conjectures are true. - N. J. A. Sloane, Jan 23 2016
(Conjecture) a(n) = A267610(n) + n. - Gus Wiseman, Mar 31 2019

A325106 Number of divisible binary-containment pairs of positive integers up to n.

Original entry on oeis.org

0, 0, 0, 1, 1, 2, 3, 4, 4, 5, 6, 7, 8, 9, 10, 13, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 26, 27, 28, 31, 32, 32, 33, 34, 35, 36, 37, 38, 40, 41, 42, 43, 44, 45, 48, 49, 50, 51, 52, 53, 56, 57, 58, 61, 63, 64, 65, 66, 67, 70, 71, 72, 77, 77, 78, 79, 80, 81
Offset: 0

Views

Author

Gus Wiseman, Mar 28 2019

Keywords

Comments

A pair of positive integers is divisible if the first divides the second, and is a binary containment if the positions of 1's in the reversed binary expansion of the first are a subset of the positions of 1's in the reversed binary expansion of the second.

Examples

			The a(3) = 1 through a(12) = 8 pairs:
  {1,3}  {1,3}  {1,3}  {1,3}  {1,3}  {1,3}  {1,3}  {1,3}   {1,3}   {1,3}
                {1,5}  {1,5}  {1,5}  {1,5}  {1,5}  {1,5}   {1,5}   {1,5}
                       {2,6}  {1,7}  {1,7}  {1,7}  {1,7}   {1,7}   {1,7}
                              {2,6}  {2,6}  {1,9}  {1,9}   {1,9}   {1,9}
                                            {2,6}  {2,6}   {2,6}   {2,6}
                                                   {2,10}  {1,11}  {1,11}
                                                           {2,10}  {2,10}
                                                                   {4,12}
		

Crossrefs

Programs

  • Mathematica
    Table[Length[Select[Subsets[Range[n],{2}],Divisible[#[[2]],#[[1]]]&&SubsetQ[Position[Reverse[IntegerDigits[#[[2]],2]],1],Position[Reverse[IntegerDigits[#1[[1]],2]],1]]&]],{n,0,30}]

Formula

a(n) = A325101(n) - n.

A325096 Number of maximal subsets of {1...n} with no binary carries.

Original entry on oeis.org

1, 1, 1, 2, 2, 3, 4, 5, 5, 7, 9, 10, 12, 13, 14, 15, 15, 20, 25, 27, 32, 34, 36, 37, 42, 44, 46, 47, 49, 50, 51, 52, 52, 67, 82, 87, 102, 107, 112, 114, 129, 134, 139, 141, 146, 148, 150, 151, 166, 171, 176, 178, 183, 185, 187, 188, 193, 195, 197, 198, 200, 201
Offset: 0

Views

Author

Gus Wiseman, Mar 27 2019

Keywords

Comments

A binary carry of two positive integers is an overlap of the positions of 1's in their reversed binary expansion.

Examples

			The a(1) = 1 through a(9) = 7 maximal subsets:
  {1}  {12}  {3}   {34}   {25}   {16}   {7}    {78}    {69}
             {12}  {124}  {34}   {25}   {16}   {168}   {78}
                          {124}  {34}   {25}   {258}   {168}
                                 {124}  {34}   {348}   {249}
                                        {124}  {1248}  {258}
                                                       {348}
                                                       {1248}
		

Crossrefs

Programs

  • Mathematica
    binpos[n_]:=Join@@Position[Reverse[IntegerDigits[n,2]],1];
    stableQ[u_,Q_]:=!Apply[Or,Outer[#1=!=#2&&Q[#1,#2]&,u,u,1],{0,1}];
    maxim[s_]:=Complement[s,Last/@Select[Tuples[s,2],UnsameQ@@#&&SubsetQ@@#&]];
    Table[Length[maxim[Select[Subsets[Range[n]],stableQ[#,Intersection[binpos[#1],binpos[#2]]!={}&]&]]],{n,0,10}]

Formula

a(2^n - 1) = A000110(n).

Extensions

a(15)-a(61) from Alois P. Heinz, Mar 28 2019

A325110 Number of strict integer partitions of n with no binary containments.

Original entry on oeis.org

1, 1, 1, 2, 1, 2, 2, 5, 2, 3, 2, 6, 3, 6, 7, 15, 8, 10, 6, 13, 6, 10, 12, 23, 13, 16, 16, 26, 21, 30, 37, 60, 43, 52, 42, 60, 42, 50, 54, 81, 59, 60, 66, 80, 74, 86, 108, 145, 119, 125, 126, 144, 134, 140, 170, 208, 189, 193, 221, 248, 253, 292, 323, 435, 392
Offset: 0

Views

Author

Gus Wiseman, Mar 28 2019

Keywords

Comments

A pair of positive integers is a binary containment if the positions of 1's in the reversed binary expansion of the first are a subset of the positions of 1's in the reversed binary expansion of the second.

Examples

			The a(1) = 1 through a(12) = 3 partitions (A = 10, B = 11, C = 12):
  (1)  (2)  (3)   (4)  (5)   (6)   (7)    (8)   (9)   (A)   (B)    (C)
            (21)       (41)  (42)  (43)   (53)  (63)  (82)  (65)   (84)
                                   (52)         (81)        (83)   (93)
                                   (61)                     (92)
                                   (421)                    (A1)
                                                            (821)
		

Crossrefs

Programs

  • Mathematica
    binpos[n_]:=Join@@Position[Reverse[IntegerDigits[n,2]],1];
    stableQ[u_,Q_]:=!Apply[Or,Outer[#1=!=#2&&Q[#1,#2]&,u,u,1],{0,1}];
    Table[Length[Select[IntegerPartitions[n],UnsameQ@@#&&stableQ[#,SubsetQ[binpos[#1],binpos[#2]]&]&]],{n,0,30}]

A325109 Number of integer partitions of n whose distinct parts have no binary containments.

Original entry on oeis.org

1, 1, 2, 3, 4, 5, 8, 10, 12, 15, 18, 23, 28, 32, 41, 52, 57, 66, 76, 90, 99, 117, 131, 157, 172, 194, 216, 255, 276, 313, 358, 410, 447, 511, 546, 630, 677, 750, 818, 945, 990, 1108, 1200, 1338, 1429, 1606, 1713, 1928, 2062, 2263, 2412, 2725, 2847, 3142, 3389
Offset: 0

Views

Author

Gus Wiseman, Mar 28 2019

Keywords

Comments

A pair of positive integers is a binary containment if the positions of 1's in the reversed binary expansion of the first are a subset of the positions of 1's in the reversed binary expansion of the second.

Examples

			The a(1) = 1 through a(8) = 12 partitions:
  (1)  (2)   (3)    (4)     (5)      (6)       (7)        (8)
       (11)  (21)   (22)    (41)     (33)      (43)       (44)
             (111)  (211)   (221)    (42)      (52)       (53)
                    (1111)  (2111)   (222)     (61)       (422)
                            (11111)  (411)     (421)      (611)
                                     (2211)    (2221)     (2222)
                                     (21111)   (4111)     (4211)
                                     (111111)  (22111)    (22211)
                                               (211111)   (41111)
                                               (1111111)  (221111)
                                                          (2111111)
                                                          (11111111)
		

Crossrefs

Programs

  • Maple
    c:= proc() option remember; local i, x, y;
          x, y:= map(n-> Bits[Split](n), [args])[];
          for i to nops(x) do
            if x[i]=1 and y[i]=0 then return false fi
          od; true
        end:
    b:= proc(n, i, s) option remember; `if`(n=0, 1, `if`(i<1, 0,
          b(n, i-1, s)+`if`(ormap(j-> c(i, j), s), 0, add(
          b(n-i*j, i-1, s union {i}), j=1..n/i))))
        end:
    a:= n-> b(n$2, {}):
    seq(a(n), n=0..55);  # Alois P. Heinz, Mar 29 2019
  • Mathematica
    binpos[n_]:=Join@@Position[Reverse[IntegerDigits[n,2]],1];
    stableQ[u_,Q_]:=!Apply[Or,Outer[#1=!=#2&&Q[#1,#2]&,u,u,1],{0,1}];
    Table[Length[Select[IntegerPartitions[n],stableQ[#,SubsetQ[binpos[#1],binpos[#2]]&]&]],{n,0,15}]
    (* Second program: *)
    c[args_List] := c[args] = Module[{i, x, y}, {x, y} = Reverse@IntegerDigits[#, 2]& /@ args; For[i = 1, i <= Length[x], i++, If[x[[i]] == 1 && y[[i]] == 0, Return[False]]]; True];
    b[n_, i_, s_List] := b[n, i, s] = If[n == 0, 1, If[i < 1, 0, b[n, i - 1, s] + If[AnyTrue[s, c[{i, #}]&], 0, Sum[b[n - i*j, i-1, s ~Union~ {i}], {j, 1, n/i}]]]];
    a[n_] := b[n, n, {}];
    a /@ Range[0, 55] (* Jean-François Alcover, Jun 03 2021, after Alois P. Heinz *)

Extensions

a(31)-a(54) from Alois P. Heinz, Mar 29 2019

A325107 Number of subsets of {1...n} with no binary containments.

Original entry on oeis.org

1, 2, 4, 5, 10, 13, 18, 19, 38, 52, 77, 83, 133, 147, 166, 167, 334, 482, 764, 848, 1465, 1680, 1987, 2007, 3699, 4413, 5488, 5572, 7264, 7412, 7579, 7580, 15160, 22573, 37251, 42824, 77387, 92863, 116453, 118461, 227502, 286775, 382573, 392246, 555661, 574113
Offset: 0

Views

Author

Gus Wiseman, Mar 28 2019

Keywords

Comments

A pair of positive integers is a binary containment if the positions of 1's in the reversed binary expansion of the first are a subset of the positions of 1's in the reversed binary expansion of the second.

Examples

			The a(0) = 1 through a(6) = 18 subsets:
  {}  {}   {}     {}     {}       {}       {}
      {1}  {1}    {1}    {1}      {1}      {1}
           {2}    {2}    {2}      {2}      {2}
           {1,2}  {3}    {3}      {3}      {3}
                  {1,2}  {4}      {4}      {4}
                         {1,2}    {5}      {5}
                         {1,4}    {1,2}    {6}
                         {2,4}    {1,4}    {1,2}
                         {3,4}    {2,4}    {1,4}
                         {1,2,4}  {2,5}    {1,6}
                                  {3,4}    {2,4}
                                  {3,5}    {2,5}
                                  {1,2,4}  {3,4}
                                           {3,5}
                                           {3,6}
                                           {5,6}
                                           {1,2,4}
                                           {3,5,6}
		

Crossrefs

Programs

  • Maple
    c:= proc() option remember; local i, x, y;
          x, y:= map(n-> Bits[Split](n), [args])[];
          for i to nops(x) do
            if x[i]=1 and y[i]=0 then return false fi
          od; true
        end:
    b:= proc(n, s) option remember; `if`(n=0, 1, b(n-1, s)+
         `if`(ormap(i-> c(n, i), s), 0, b(n-1, s union {n})))
        end:
    a:= n-> b(n, {}):
    seq(a(n), n=0..34);  # Alois P. Heinz, Mar 28 2019
  • Mathematica
    binpos[n_]:=Join@@Position[Reverse[IntegerDigits[n,2]],1];
    stableQ[u_,Q_]:=!Apply[Or,Outer[#1=!=#2&&Q[#1,#2]&,u,u,1],{0,1}];
    Table[Length[Select[Subsets[Range[n]],stableQ[#,SubsetQ[binpos[#1],binpos[#2]]&]&]],{n,0,13}]

Formula

a(2^n - 1) = A014466(n).

Extensions

a(16)-a(45) from Alois P. Heinz, Mar 28 2019

A325108 Number of maximal subsets of {1...n} with no binary containments.

Original entry on oeis.org

1, 1, 1, 2, 2, 4, 5, 6, 6, 11, 13, 16, 17, 22, 27, 28
Offset: 0

Views

Author

Gus Wiseman, Mar 28 2019

Keywords

Comments

A pair of positive integers is a binary containment if the positions of 1's in the reversed binary expansion of the first are a subset of the positions of 1's in the reversed binary expansion of the second.

Examples

			The a(0) = 1 through a(7) = 6 maximal subsets:
  {}  {1}  {1,2}  {3}    {3,4}    {2,5}    {1,6}    {7}
                  {1,2}  {1,2,4}  {3,4}    {2,5}    {1,6}
                                  {3,5}    {3,4}    {2,5}
                                  {1,2,4}  {1,2,4}  {3,4}
                                           {3,5,6}  {1,2,4}
                                                    {3,5,6}
		

Crossrefs

Programs

  • Mathematica
    binpos[n_]:=Join@@Position[Reverse[IntegerDigits[n,2]],1];
    stableQ[u_,Q_]:=!Apply[Or,Outer[#1=!=#2&&Q[#1,#2]&,u,u,1],{0,1}];
    maxim[s_]:=Complement[s,Last/@Select[Tuples[s,2],UnsameQ@@#&&SubsetQ@@#&]];
    Table[Length[maxim[Select[Subsets[Range[n]],stableQ[#,SubsetQ[binpos[#1],binpos[#2]]&]&]]],{n,0,10}]

A325123 Number of divisible pairs of positive integers up to n with no binary carries.

Original entry on oeis.org

0, 0, 1, 1, 3, 3, 4, 4, 7, 7, 9, 9, 12, 12, 13, 13, 17, 17, 19, 19, 22, 22, 23, 23, 28, 28, 29, 29, 31, 31, 32, 32, 37, 37, 39, 39, 44, 44, 45, 45, 50, 50, 52, 52, 54, 54, 55, 55, 62, 62, 64, 64, 66, 66, 68, 68, 72, 72, 73, 73, 76, 76, 77, 77, 83, 83, 85, 85
Offset: 0

Views

Author

Gus Wiseman, Mar 29 2019

Keywords

Comments

Two positive integers are divisible if the first divides the second, and they have a binary carry if the positions of 1's in their reversed binary expansion overlap.
a(2k+1) = a(2k), since an odd number and any divisor will overlap in the last digit. Additionally, a(2k+2) > a(2k+1) because the pair {1,2k+2} is always valid. Therefore, every term appears exactly twice. - Charlie Neder, Apr 02 2019

Examples

			The a(2) = 1 through a(11) = 9 pairs:
  {1,2}  {1,2}  {1,2}  {1,2}  {1,2}  {1,2}  {1,2}  {1,2}  {1,2}   {1,2}
                {1,4}  {1,4}  {1,4}  {1,4}  {1,4}  {1,4}  {1,4}   {1,4}
                {2,4}  {2,4}  {1,6}  {1,6}  {1,6}  {1,6}  {1,6}   {1,6}
                              {2,4}  {2,4}  {1,8}  {1,8}  {1,8}   {1,8}
                                            {2,4}  {2,4}  {2,4}   {2,4}
                                            {2,8}  {2,8}  {2,8}   {2,8}
                                            {4,8}  {4,8}  {4,8}   {4,8}
                                                          {1,10}  {1,10}
                                                          {5,10}  {5,10}
		

Crossrefs

Programs

  • Mathematica
    Table[Length[Select[Tuples[Range[n],2],Divisible@@Reverse[#]&&Intersection[Position[Reverse[IntegerDigits[#[[1]],2]],1],Position[Reverse[IntegerDigits[#[[2]],2]],1]]=={}&]],{n,0,20}]

A325100 Heinz numbers of strict integer partitions with no binary carries.

Original entry on oeis.org

1, 2, 3, 5, 6, 7, 11, 13, 14, 17, 19, 21, 23, 26, 29, 31, 33, 35, 37, 38, 41, 42, 43, 47, 53, 57, 58, 59, 61, 67, 69, 71, 73, 74, 79, 83, 86, 89, 95, 97, 101, 103, 106, 107, 109, 111, 113, 114, 122, 123, 127, 131, 133, 137, 139, 142, 149, 151, 157, 158, 159
Offset: 1

Views

Author

Gus Wiseman, Mar 28 2019

Keywords

Comments

A binary carry of two positive integers is an overlap of the positions of 1's in their reversed binary expansion.
The Heinz number of an integer partition (y_1,...,y_k) is prime(y_1) * ... * prime(y_k), so these are squarefree numbers whose prime indices have no carries. A prime index of n is a number m such that prime(m) divides n. The multiset of prime indices of n is row n of A112798.

Examples

			The sequence of terms together with their prime indices begins:
   1: {}
   2: {1}
   3: {2}
   5: {3}
   6: {1,2}
   7: {4}
  11: {5}
  13: {6}
  14: {1,4}
  17: {7}
  19: {8}
  21: {2,4}
  23: {9}
  26: {1,6}
  29: {10}
  31: {11}
  33: {2,5}
  35: {3,4}
  37: {12}
  38: {1,8}
  41: {13}
  42: {1,2,4}
		

Crossrefs

Programs

  • Mathematica
    binpos[n_]:=Join@@Position[Reverse[IntegerDigits[n,2]],1];
    stableQ[u_,Q_]:=!Apply[Or,Outer[#1=!=#2&&Q[#1,#2]&,u,u,1],{0,1}];
    Select[Range[100],SquareFreeQ[#]&&stableQ[PrimePi/@First/@FactorInteger[#],Intersection[binpos[#1],binpos[#2]]!={}&]&]
Showing 1-10 of 12 results. Next