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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A306417 Number of self-conjugate set partitions of {1, ..., n}.

Original entry on oeis.org

1, 1, 0, 1, 1, 2, 7, 7, 46, 39, 321
Offset: 0

Views

Author

Gus Wiseman, Feb 14 2019

Keywords

Comments

This sequence counts set partitions fixed under Callan's conjugation operation.

Examples

			The  a(3) = 1 through a(7) = 7 self-conjugate set partitions:
  {{12}{3}}  {{13}{24}}  {{123}{4}{5}}  {{135}{246}}    {{13}{246}{57}}
                         {{13}{2}{45}}  {{124}{35}{6}}  {{15}{246}{37}}
                                        {{13}{25}{46}}  {{1234}{5}{6}{7}}
                                        {{14}{2}{356}}  {{124}{3}{56}{7}}
                                        {{14}{236}{5}}  {{134}{2}{5}{67}}
                                        {{14}{25}{36}}  {{14}{2}{3}{567}}
                                        {{145}{26}{3}}  {{14}{23}{57}{6}}
		

Crossrefs

A324012 Number of self-complementary set partitions of {1, ..., n} with no singletons or cyclical adjacencies (successive elements in the same block, where 1 is a successor of n).

Original entry on oeis.org

1, 0, 0, 0, 1, 0, 3, 2, 14, 11, 80, 85, 510
Offset: 0

Views

Author

Gus Wiseman, Feb 12 2019

Keywords

Comments

The complement of a set partition pi of {1, ..., n} is defined as n + 1 - pi (elementwise) on page 3 of Callan. For example, the complement of {{1,5},{2},{3,6},{4}} is {{1,4},{2,6},{3},{5}}. This sequence counts certain self-conjugate set partitions, i.e., fixed points under Callan's conjugation operation.

Examples

			The  a(6) = 3 through a(9) = 11 self-complementary set partitions with no singletons or cyclical adjacencies:
  {{135}{246}}    {{13}{246}{57}}  {{1357}{2468}}      {{136}{258}{479}}
  {{13}{25}{46}}  {{15}{246}{37}}  {{135}{27}{468}}    {{147}{258}{369}}
  {{14}{25}{36}}                   {{146}{27}{358}}    {{148}{269}{357}}
                                   {{147}{258}{36}}    {{168}{249}{357}}
                                   {{157}{248}{36}}    {{13}{258}{46}{79}}
                                   {{13}{24}{57}{68}}  {{14}{258}{37}{69}}
                                   {{13}{25}{47}{68}}  {{14}{28}{357}{69}}
                                   {{14}{26}{37}{58}}  {{16}{258}{37}{49}}
                                   {{14}{27}{36}{58}}  {{16}{28}{357}{49}}
                                   {{15}{26}{37}{48}}  {{17}{258}{39}{46}}
                                   {{15}{27}{36}{48}}  {{18}{29}{357}{46}}
                                   {{16}{24}{38}{57}}
                                   {{16}{25}{38}{47}}
                                   {{17}{28}{35}{46}}
		

Crossrefs

Cf. A000110, A000126, A000296, A001610, A080107, A169985, A261139, A306417 (all self-conjugate set partitions), A324011 (self-complementarity not required), A324013 (adjacencies allowed), A324014 (singletons allowed), A324015.

Programs

  • Mathematica
    sps[{}]:={{}};sps[set:{i_,_}]:=Join@@Function[s,Prepend[#,s]&/@sps[Complement[set,s]]]/@Cases[Subsets[set],{i,_}];
    cmp[stn_]:=Union[Sort[Max@@Join@@stn+1-#]&/@stn];
    Table[Select[sps[Range[n]],And[cmp[#]==Sort[#],Count[#,{_}]==0,Total[If[First[#]==1&&Last[#]==n,1,0]+Count[Subtract@@@Partition[#,2,1],-1]&/@#]==0]&]//Length,{n,0,10}]

A222334 T(n,k)=Number of binary arrays indicating the locations of trailing edge maxima of a random length-n 0..k array extended with zeros and convolved with 1,1.

Original entry on oeis.org

2, 2, 3, 2, 3, 4, 2, 3, 4, 6, 2, 3, 4, 7, 9, 2, 3, 4, 7, 11, 13, 2, 3, 4, 7, 11, 17, 19, 2, 3, 4, 7, 11, 18, 27, 28, 2, 3, 4, 7, 11, 18, 29, 42, 41, 2, 3, 4, 7, 11, 18, 29, 46, 66, 60, 2, 3, 4, 7, 11, 18, 29, 47, 74, 104, 88, 2, 3, 4, 7, 11, 18, 29, 47, 76, 118, 163, 129, 2, 3, 4, 7, 11, 18, 29, 47
Offset: 1

Views

Author

R. H. Hardin Feb 15 2013

Keywords

Comments

Table starts
....2....2.....2.....2.....2.....2.....2.....2.....2.....2.....2
....3....3.....3.....3.....3.....3.....3.....3.....3.....3.....3
....4....4.....4.....4.....4.....4.....4.....4.....4.....4.....4
....6....7.....7.....7.....7.....7.....7.....7.....7.....7.....7
....9...11....11....11....11....11....11....11....11....11....11
...13...17....18....18....18....18....18....18....18....18....18
...19...27....29....29....29....29....29....29....29....29....29
...28...42....46....47....47....47....47....47....47....47....47
...41...66....74....76....76....76....76....76....76....76....76
...60..104...118...122...123...123...123...123...123...123...123
...88..163...189...197...199...199...199...199...199...199...199
..129..256...303...317...321...322...322...322...322...322...322
..189..402...485...511...519...521...521...521...521...521...521
..277..631...777...824...838...842...843...843...843...843...843
..406..991..1244..1328..1354..1362..1364..1364..1364..1364..1364
..595.1556..1992..2141..2188..2202..2206..2207..2207..2207..2207
..872.2443..3190..3451..3535..3561..3569..3571..3571..3571..3571
.1278.3836..5108..5563..5712..5759..5773..5777..5778..5778..5778
.1873.6023..8180..8967..9229..9313..9339..9347..9349..9349..9349
.2745.9457.13099.14454.14912.15061.15108.15122.15126.15127.15127
Empirical: for n<=2k+1, T(n,k)=A080023(n)=A169985(n), which is A000032(n) for n>=2. - Danny Rorabaugh, Mar 13 2015

Examples

			Some solutions for n=6 k=4, one extended zero followed by filtered positions
..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0
..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0
..0....0....1....0....1....0....1....0....1....0....0....1....0....1....0....0
..0....0....0....1....0....0....0....1....0....0....0....0....0....0....1....1
..0....1....1....0....0....1....0....0....1....0....0....0....1....0....0....0
..0....0....0....0....0....0....0....0....0....1....0....0....0....1....1....0
..0....1....0....0....1....0....0....1....1....0....1....0....0....0....0....0
..1....0....0....1....0....1....1....0....0....0....0....0....0....0....0....0
		

Crossrefs

Column 1 is A000930(n+2).
Column 2 is A222122.
Columns 3 to 7 are A222329 to A222333.

Formula

Empirical for column k:
k=1: a(n) = a(n-1)+a(n-3)
k=2: a(n) = a(n-1)+a(n-3)+a(n-5)
k=3: a(n) = a(n-1)+a(n-3)+a(n-5)+a(n-7)
k=4: a(n) = a(n-1)+a(n-3)+a(n-5)+a(n-7)+a(n-9)
k=5: a(n) = a(n-1)+a(n-3)+a(n-5)+a(n-7)+a(n-9)+a(n-11)
k=6: a(n) = a(n-1)+a(n-3)+a(n-5)+a(n-7)+a(n-9)+a(n-11)+a(n-13)
k=7: a(n) = a(n-1)+a(n-3)+a(n-5)+a(n-7)+a(n-9)+a(n-11)+a(n-13)+a(n-15)

A163733 Number of n X 2 binary arrays with all 1's connected, all corners 1, and no 1 having more than two 1's adjacent.

Original entry on oeis.org

1, 1, 2, 2, 4, 6, 10, 16, 26, 42, 68, 110, 178, 288, 466, 754, 1220, 1974, 3194, 5168, 8362, 13530, 21892, 35422, 57314, 92736, 150050, 242786, 392836, 635622, 1028458, 1664080, 2692538, 4356618, 7049156, 11405774, 18454930, 29860704, 48315634, 78176338
Offset: 1

Views

Author

R. H. Hardin, Aug 03 2009

Keywords

Comments

Same recurrence for A163695.
Same recurrence for A163714.
Appears to coincide with diagonal sums of A072405. - Paul Barry, Aug 10 2009
From Gary W. Adamson, Sep 15 2016: (Start)
Let the sequence prefaced with a 1: (1, 1, 1, 2, 2, 4, 6, ...) equate to r(x). Then (r(x) * r(x^2) * r(x^4) * r(x^8) * ...) = the Fibonacci sequence, (1, 1, 2, 3, 5, ...). Let M = the following production matrix:
1, 0, 0, 0, 0, ...
1, 0, 0, 0, 0, ...
1, 1, 0, 0, 0, ...
2, 1, 0, 0, 0, ...
2, 1, 1, 0, 0, ...
4, 2, 1, 0, 0, ...
6, 2, 1, 1, 0, ...
...
Limit of the matrix power M^k as k->infinity results in a single column vector equal to the Fibonacci sequence. (End)
Apparently a(n) = A128588(n-2) for n > 3. - Georg Fischer, Oct 14 2018

Examples

			All solutions for n=8:
   1 1   1 1   1 1   1 1   1 1   1 1   1 1   1 1   1 1   1 1
   0 1   1 0   1 0   1 0   1 0   1 0   0 1   0 1   0 1   0 1
   0 1   1 0   1 0   1 0   1 1   1 0   0 1   0 1   1 1   0 1
   0 1   1 0   1 0   1 1   0 1   1 0   0 1   0 1   1 0   1 1
   0 1   1 0   1 1   0 1   0 1   1 0   0 1   1 1   1 0   1 0
   0 1   1 0   0 1   0 1   0 1   1 1   1 1   1 0   1 0   1 0
   0 1   1 0   0 1   0 1   0 1   0 1   1 0   1 0   1 0   1 0
   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
   0 1   0 1   0 1   1 0   1 0   1 0
   1 1   1 1   0 1   1 0   1 1   1 1
   1 0   1 0   1 1   1 1   0 1   0 1
   1 1   1 0   1 0   0 1   0 1   1 1
   0 1   1 1   1 1   1 1   1 1   1 0
   0 1   0 1   0 1   1 0   1 0   1 0
   1 1   1 1   1 1   1 1   1 1   1 1
		

Crossrefs

Programs

Formula

Empirical: a(n) = a(n-1) + a(n-2) for n >= 5.
G.f.: (1-x^3)/(1-x-x^2) (conjecture). - Paul Barry, Aug 10 2009
a(n) = round(phi^(k-1)) - round(phi^(k-1)/sqrt(5)), phi = (1 + sqrt(5))/2 (conjecture). - Federico Provvedi, Mar 26 2013
G.f.: 1 + 2*x - x*Q(0), where Q(k) = 1 + x^2 - (2*k+1)*x + x*(2*k-1 - x)/Q(k+1); (conjecture), (continued fraction). - Sergei N. Gladkovskii, Oct 05 2013
G.f.: If prefaced with a 1, (1, 1, 1, 2, 2, 4, ...): (1 - x^2 - x^4)/(1 - x - x^2); where the modified sequence satisfies A(x)/A(x^2), A(x) is the Fibonacci sequence. - Gary W. Adamson, Sep 15 2016

A306357 Number of nonempty subsets of {1, ..., n} containing no three cyclically successive elements.

Original entry on oeis.org

0, 1, 3, 6, 10, 20, 38, 70, 130, 240, 442, 814, 1498, 2756, 5070, 9326, 17154, 31552, 58034, 106742, 196330, 361108, 664182, 1221622, 2246914, 4132720, 7601258, 13980894, 25714874, 47297028, 86992798, 160004702, 294294530, 541292032, 995591266, 1831177830
Offset: 0

Views

Author

Gus Wiseman, Feb 10 2019

Keywords

Comments

Cyclically successive means 1 is a successor of n.
Set partitions using these subsets are counted by A323949.

Examples

			The a(1) = 1 through a(5) = 20 stable subsets:
  {1}  {1}    {1}    {1}    {1}
       {2}    {2}    {2}    {2}
       {1,2}  {3}    {3}    {3}
              {1,2}  {4}    {4}
              {1,3}  {1,2}  {5}
              {2,3}  {1,3}  {1,2}
                     {1,4}  {1,3}
                     {2,3}  {1,4}
                     {2,4}  {1,5}
                     {3,4}  {2,3}
                            {2,4}
                            {2,5}
                            {3,4}
                            {3,5}
                            {4,5}
                            {1,2,4}
                            {1,3,4}
                            {1,3,5}
                            {2,3,5}
                            {2,4,5}
		

Crossrefs

Programs

  • Mathematica
    stabsubs[g_]:=Select[Rest[Subsets[Union@@g]],Select[g,Function[ed,UnsameQ@@ed&&Complement[ed,#]=={}]]=={}&];
    Table[Length[stabsubs[Partition[Range[n],3,1,1]]],{n,15}]

Formula

For n >= 3 we have a(n) = A001644(n) - 1.
From Chai Wah Wu, Jan 06 2020: (Start)
a(n) = 2*a(n-1) - a(n-4) for n > 6.
G.f.: x*(x^5 + x^4 - 2*x^3 + x + 1)/(x^4 - 2*x + 1). (End)

A324014 Number of self-complementary set partitions of {1, ..., n} with no cyclical adjacencies (successive elements in the same block, where 1 is a successor of n).

Original entry on oeis.org

1, 0, 1, 1, 2, 3, 9, 16, 43, 89, 250, 571, 1639
Offset: 0

Views

Author

Gus Wiseman, Feb 12 2019

Keywords

Comments

The complement of a set partition pi of {1, ..., n} is defined as n + 1 - pi (elementwise) on page 3 of Callan. For example, the complement of {{1,5},{2},{3,6},{4}} is {{1,4},{2,6},{3},{5}}.

Examples

			The  a(3) = 1 through a(6) = 9 self-complementary set partitions with no cyclical adjacencies:
  {{1}{2}{3}}  {{13}{24}}      {{14}{25}{3}}      {{135}{246}}
               {{1}{2}{3}{4}}  {{1}{24}{3}{5}}    {{13}{25}{46}}
                               {{1}{2}{3}{4}{5}}  {{14}{25}{36}}
                                                  {{1}{24}{35}{6}}
                                                  {{13}{2}{46}{5}}
                                                  {{14}{2}{36}{5}}
                                                  {{15}{26}{3}{4}}
                                                  {{1}{25}{3}{4}{6}}
                                                  {{1}{2}{3}{4}{5}{6}}
		

Crossrefs

Cf. A000110, A000296, A001610, A080107 (self-complementary), A169985, A324012 (self-conjugate), A324015.

Programs

  • Mathematica
    sps[{}]:={{}};sps[set:{i_,_}]:=Join@@Function[s,Prepend[#,s]&/@sps[Complement[set,s]]]/@Cases[Subsets[set],{i,_}];
    cmp[stn_]:=Union[Sort[Max@@Join@@stn+1-#]&/@stn];
    Table[Select[sps[Range[n]],And[cmp[#]==Sort[#],Total[If[First[#]==1&&Last[#]==n,1,0]+Count[Subtract@@@Partition[#,2,1],-1]&/@#]==0]&]//Length,{n,0,10}]

A324015 Number of nonempty subsets of {1, ..., n} containing no two cyclically successive elements.

Original entry on oeis.org

0, 1, 2, 3, 6, 10, 17, 28, 46, 75, 122, 198, 321, 520, 842, 1363, 2206, 3570, 5777, 9348, 15126, 24475, 39602, 64078, 103681, 167760, 271442, 439203, 710646, 1149850, 1860497, 3010348, 4870846, 7881195, 12752042, 20633238, 33385281, 54018520, 87403802
Offset: 0

Views

Author

Gus Wiseman, Feb 12 2019

Keywords

Comments

Cyclically successive means 1 succeeds n.
After a(1) = 1, same as A001610 shifted once to the right. Also, a(n) = A169985(n) - 1.

Examples

			The a(6) = 17 stable subsets:
  {1}, {2}, {3}, {4}, {5}, {6},
  {1,3}, {1,4}, {1,5}, {2,4}, {2,5}, {2,6}, {3,5}, {3,6}, {4,6},
  {1,3,5}, {2,4,6}.
		

Crossrefs

Programs

  • Mathematica
    stabsubs[g_]:=Select[Rest[Subsets[Union@@g]],Select[g,Function[ed,UnsameQ@@ed&&Complement[ed,#]=={}]]=={}&];
    Table[Length[stabsubs[Partition[Range[n],2,1,1]]],{n,0,10}]

Formula

For n <= 3, a(n) = n. Otherwise, a(n) = a(n - 1) + a(n - 2) + 1.

A062724 a(n) = floor(tau^n) + 1, where tau = (1 + sqrt(5))/2.

Original entry on oeis.org

2, 2, 3, 5, 7, 12, 18, 30, 47, 77, 123, 200, 322, 522, 843, 1365, 2207, 3572, 5778, 9350, 15127, 24477, 39603, 64080, 103682, 167762, 271443, 439205, 710647, 1149852, 1860498, 3010350, 4870847, 7881197, 12752043, 20633240, 33385282
Offset: 0

Views

Author

Jason Earls, Jul 15 2001

Keywords

Comments

Apart from the first term, this sequence also gives the ceiling of the powers of the golden ratio (cf. A169986). - Mohammad K. Azarian, Apr 14 2008

Crossrefs

Equals A014217 + 1.

Programs

  • Mathematica
    Floor[GoldenRatio^Range[0,40]]+1 (* Harvey P. Dale, Dec 18 2019 *)
  • PARI
    j=[]; for(n=0,60,t=(1+sqrt(5))/2; j=concat(j,floor((t^n))+1)); j
    
  • PARI
    { default(realprecision, 200); t=(1 + sqrt(5))/2; p=1; for (n=0, 400, if (n, p*=t); write("b062724.txt", n, " ", p\1 + 1) ) } \\ Harry J. Smith, Aug 09 2009

Formula

a(n) = 3*Fibonacci(n-1) + Fibonacci(n-2) + (n mod 2), n > 0. - Gary Detlefs, Dec 29 2010

A205579 a(n) = round(r^n) where r is the smallest Pisot number (real root r=1.3247179.. of x^3-x-1).

Original entry on oeis.org

1, 1, 2, 2, 3, 4, 5, 7, 9, 13, 17, 22, 29, 39, 51, 68, 90, 119, 158, 209, 277, 367, 486, 644, 853, 1130, 1497, 1983, 2627, 3480, 4610, 6107, 8090, 10717, 14197, 18807, 24914, 33004, 43721, 57918, 76725, 101639, 134643, 178364, 236282, 313007, 414646, 549289, 727653, 963935, 1276942, 1691588, 2240877, 2968530, 3932465
Offset: 0

Views

Author

Joerg Arndt, Jan 29 2012

Keywords

Crossrefs

Cf. A112639 (definition using floor() instead of round()).
Cf. A060006 (decimal expansion of r=1.32471795724475...).

Programs

  • Mathematica
    CoefficientList[Series[(1+x+x^2+x^9+x^10-x^12)/(1-x^2-x^3),{x,0,100}],x] (* Vincenzo Librandi, Aug 19 2012 *)
    r = Root[x^3-x-1, 1]; Table[Round[r^i], {i,0,100 }] (* Jwalin Bhatt, Mar 27 2025 *)
  • PARI
    default(realprecision, 110);
    default(format, "g.15");
    r=real(polroots(x^3-x-1)[1])
    v=vector(66, n, round(r^(n-1)) )
    
  • PARI
    Vec((1+x+x^2+x^9+x^10-x^12)/(1-x^2-x^3)+O(x^66))

Formula

G.f.: (1+x+x^2+x^9+x^10-x^12)/(1-x^2-x^3).
From Jwalin Bhatt, Mar 26 2025: (Start)
a(n) = round(((1/2+sqrt(23/108))^(1/3) + (1/2-sqrt(23/108))^(1/3))^n).
a(n) = a(n-2) + a(n-3) for n>=13. (End)

A323949 Number of set partitions of {1, ..., n} with no block containing three distinct cyclically successive vertices.

Original entry on oeis.org

1, 1, 2, 4, 10, 36, 145, 631, 3015, 15563, 86144, 508311, 3180930, 21018999, 146111543, 1065040886, 8117566366, 64531949885, 533880211566, 4587373155544, 40865048111424, 376788283806743, 3590485953393739, 35312436594162173, 357995171351223109, 3736806713651177702
Offset: 0

Views

Author

Gus Wiseman, Feb 10 2019

Keywords

Comments

Cyclically successive means 1 is a successor of n.

Examples

			The a(1) = 1 through a(4) = 10 set partitions:
  {{1}}  {{1,2}}    {{1},{2,3}}    {{1,2},{3,4}}
         {{1},{2}}  {{1,2},{3}}    {{1,3},{2,4}}
                    {{1,3},{2}}    {{1,4},{2,3}}
                    {{1},{2},{3}}  {{1},{2},{3,4}}
                                   {{1},{2,3},{4}}
                                   {{1,2},{3},{4}}
                                   {{1},{2,4},{3}}
                                   {{1,3},{2},{4}}
                                   {{1,4},{2},{3}}
                                   {{1},{2},{3},{4}}
		

Crossrefs

Programs

  • Mathematica
    spsu[,{}]:={{}};spsu[foo,set:{i_,_}]:=Join@@Function[s,Prepend[#,s]&/@spsu[Select[foo,Complement[#,Complement[set,s]]=={}&],Complement[set,s]]]/@Cases[foo,{i,_}];
    Table[Length[spsu[Select[Subsets[Range[n]],Select[Partition[Range[n],3,1,1],Function[ed,UnsameQ@@ed&&Complement[ed,#]=={}]]=={}&],Range[n]]],{n,8}]

Extensions

a(12)-a(25) from Alois P. Heinz, Feb 10 2019
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