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 1-7 of 7 results.

A050315 Main diagonal of A050314.

Original entry on oeis.org

1, 1, 1, 2, 1, 2, 2, 5, 1, 2, 2, 5, 2, 5, 5, 15, 1, 2, 2, 5, 2, 5, 5, 15, 2, 5, 5, 15, 5, 15, 15, 52, 1, 2, 2, 5, 2, 5, 5, 15, 2, 5, 5, 15, 5, 15, 15, 52, 2, 5, 5, 15, 5, 15, 15, 52, 5, 15, 15, 52, 15, 52, 52, 203, 1, 2, 2, 5, 2, 5, 5, 15, 2, 5, 5, 15, 5, 15, 15, 52, 2, 5, 5, 15, 5, 15
Offset: 0

Views

Author

Christian G. Bower, Sep 15 1999

Keywords

Comments

Also, a(n) is the number of odd multinomial coefficients n!/(k_1!...k_m!) with 1 <= k_1 <= ... <= k_m and k_1 + ... + k_m = n. - Pontus von Brömssen, Mar 23 2018
From Gus Wiseman, Mar 30 2019: (Start)
Also the number of strict integer partitions of n with no binary carries. The Heinz numbers of these partitions are given by A325100. A binary carry of two positive integers is an overlap of the positions of 1's in their reversed binary expansion. For example, the a(1) = 1 through a(15) = 15 strict integer partitions with no binary carries are:
(1) (2) (3) (4) (5) (6) (7) (8) (9) (A) (B) (C) (D) (E) (F)
(21) (41) (42) (43) (81) (82) (83) (84) (85) (86) (87)
(52) (92) (94) (A4) (96)
(61) (A1) (C1) (C2) (A5)
(421) (821) (841) (842) (B4)
(C3)
(D2)
(E1)
(843)
(852)
(861)
(942)
(A41)
(C21)
(8421)
(End)

Crossrefs

Programs

  • Maple
    a:= n-> combinat[bell](add(i,i=convert(n, base, 2))):
    seq(a(n), n=0..100);  # Alois P. Heinz, Apr 08 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],UnsameQ@@#&&stableQ[#,Intersection[binpos[#1],binpos[#2]]!={}&]&]],{n,0,20}] (* Gus Wiseman, Mar 30 2019 *)
    a[n_] := BellB[DigitCount[n, 2, 1]];
    a /@ Range[0, 100] (* Jean-François Alcover, May 21 2021 *)

Formula

Bell number of number of 1's in binary: a(n) = A000110(A000120(n)).

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

A325103 Number of increasing pairs of positive integers up to n with no binary carries.

Original entry on oeis.org

0, 0, 1, 1, 4, 5, 6, 6, 13, 16, 19, 20, 23, 24, 25, 25, 40, 47, 54, 57, 64, 67, 70, 71, 78, 81, 84, 85, 88, 89, 90, 90, 121, 136, 151, 158, 173, 180, 187, 190, 205, 212, 219, 222, 229, 232, 235, 236, 251, 258, 265, 268, 275, 278, 281, 282, 289, 292, 295, 296
Offset: 0

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.

Examples

			The a(2) = 1 through a(9) = 16 pairs:
  {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}
                {2,4}  {2,4}  {1,6}  {1,6}  {1,6}  {1,6}
                {3,4}  {2,5}  {2,4}  {2,4}  {1,8}  {1,8}
                       {3,4}  {2,5}  {2,5}  {2,4}  {2,4}
                              {3,4}  {3,4}  {2,5}  {2,5}
                                            {2,8}  {2,8}
                                            {3,4}  {2,9}
                                            {3,8}  {3,4}
                                            {4,8}  {3,8}
                                            {5,8}  {4,8}
                                            {6,8}  {4,9}
                                            {7,8}  {5,8}
                                                   {6,8}
                                                   {6,9}
                                                   {7,8}
		

Crossrefs

Programs

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

Formula

a(n) = A325102(n)/2.

A325104 Number of increasing pairs of positive integers up to n with at least one binary carry.

Original entry on oeis.org

0, 0, 0, 2, 2, 5, 9, 15, 15, 20, 26, 35, 43, 54, 66, 80, 80, 89, 99, 114, 126, 143, 161, 182, 198, 219, 241, 266, 290, 317, 345, 375, 375, 392, 410, 437, 457, 486, 516, 551, 575, 608, 642, 681, 717, 758, 800, 845, 877, 918, 960, 1007, 1051, 1100, 1150, 1203
Offset: 0

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 version for ordered pairs is A080572.

Examples

			The a(3) = 2 through a(8) = 15 pairs:
  {1,3}  {1,3}  {1,3}  {1,3}  {1,3}  {1,3}
  {2,3}  {2,3}  {1,5}  {1,5}  {1,5}  {1,5}
                {2,3}  {2,3}  {1,7}  {1,7}
                {3,5}  {2,6}  {2,3}  {2,3}
                {4,5}  {3,5}  {2,6}  {2,6}
                       {3,6}  {2,7}  {2,7}
                       {4,5}  {3,5}  {3,5}
                       {4,6}  {3,6}  {3,6}
                       {5,6}  {3,7}  {3,7}
                              {4,5}  {4,5}
                              {4,6}  {4,6}
                              {4,7}  {4,7}
                              {5,6}  {5,6}
                              {5,7}  {5,7}
                              {6,7}  {6,7}
		

Crossrefs

Programs

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

Formula

a(n) = 2 * A080572(n - 2) + n.

A325102 Number of ordered pairs of positive integers up to n with no binary carries.

Original entry on oeis.org

0, 0, 2, 2, 8, 10, 12, 12, 26, 32, 38, 40, 46, 48, 50, 50, 80, 94, 108, 114, 128, 134, 140, 142, 156, 162, 168, 170, 176, 178, 180, 180, 242, 272, 302, 316, 346, 360, 374, 380, 410, 424, 438, 444, 458, 464, 470, 472, 502, 516, 530, 536, 550, 556, 562, 564, 578
Offset: 0

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.

Examples

			The a(2) = 2 through a(6) = 12 pairs:
  (1,2)  (1,2)  (1,2)  (1,2)  (1,2)  (1,2)
  (2,1)  (2,1)  (1,4)  (1,4)  (1,4)  (1,4)
                (2,1)  (2,1)  (1,6)  (1,6)
                (2,4)  (2,4)  (2,1)  (2,1)
                (3,4)  (2,5)  (2,4)  (2,4)
                (4,1)  (3,4)  (2,5)  (2,5)
                (4,2)  (4,1)  (3,4)  (3,4)
                (4,3)  (4,2)  (4,1)  (4,1)
                       (4,3)  (4,2)  (4,2)
                       (5,2)  (4,3)  (4,3)
                              (5,2)  (5,2)
                              (6,1)  (6,1)
		

Crossrefs

Programs

  • Mathematica
    Table[Length[Select[Tuples[Range[n],2],Intersection[Position[Reverse[IntegerDigits[#[[1]],2]],1],Position[Reverse[IntegerDigits[#[[2]],2]],1]]=={}&]],{n,0,30}]

Formula

a(n) = 2 * A325103(n).

A325124 Number of divisible pairs of positive integers up to n with at least one binary carry.

Original entry on oeis.org

0, 1, 2, 4, 5, 7, 10, 12, 13, 16, 18, 20, 23, 25, 28, 32, 33, 35, 39, 41, 44, 48, 51, 53, 56, 59, 62, 66, 70, 72, 79, 81, 82, 86, 88, 92, 96, 98, 101, 105, 108, 110, 116, 118, 122, 128, 131, 133, 136, 139, 143, 147, 151, 153, 159, 163, 167, 171, 174, 176, 185
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.

Examples

			The a(1) = 1 through a(8) = 13 pairs:
  (1,1)  (1,1)  (1,1)  (1,1)  (1,1)  (1,1)  (1,1)  (1,1)
         (2,2)  (1,3)  (1,3)  (1,3)  (1,3)  (1,3)  (1,3)
                (2,2)  (2,2)  (1,5)  (1,5)  (1,5)  (1,5)
                (3,3)  (3,3)  (2,2)  (2,2)  (1,7)  (1,7)
                       (4,4)  (3,3)  (2,6)  (2,2)  (2,2)
                              (4,4)  (3,3)  (2,6)  (2,6)
                              (5,5)  (3,6)  (3,3)  (3,3)
                                     (4,4)  (3,6)  (3,6)
                                     (5,5)  (4,4)  (4,4)
                                     (6,6)  (5,5)  (5,5)
                                            (6,6)  (6,6)
                                            (7,7)  (7,7)
                                                   (8,8)
		

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}]

Formula

a(n) = A307230(n) + n.

A307314 Number of divisors d of 2n such that adding d to 2n in binary requires no carries.

Original entry on oeis.org

1, 2, 1, 3, 2, 3, 1, 4, 2, 3, 1, 5, 1, 2, 1, 5, 2, 5, 1, 5, 2, 2, 1, 7, 2, 2, 2, 4, 1, 3, 1, 6, 2, 4, 1, 7, 2, 3, 1, 7, 2, 4, 1, 3, 2, 2, 1, 9, 1, 4, 2, 3, 1, 4, 1, 6, 1, 2, 1, 6, 1, 2, 1, 7, 4, 6, 1, 6, 2, 3, 1, 10, 2, 3, 1, 4, 1, 3, 1, 9
Offset: 1

Views

Author

Charlie Neder, Apr 02 2019

Keywords

Comments

Equivalently, number of numbers d such that d|2n and d AND 2n = 0.
First differences of either bisection of A325123.

Crossrefs

Programs

  • Mathematica
    a[n_] := DivisorSum[2*n, 1 &, BitAnd[#, 2*n] == 0 &]; Array[a, 100] (* Amiram Eldar, Feb 08 2025 *)
  • PARI
    a(n) = sumdiv(2*n, d, bitand(d, 2*n) == 0); \\ Michel Marcus, Apr 02 2019

Formula

A001511(n) <= a(n) <= A000005(n).
a(p) = 1 + [p is in A247068] for p prime, where [] is the Iverson bracket.
Showing 1-7 of 7 results.