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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A244164 Number of compositions of n in which the minimal multiplicity of parts equals 1.

Original entry on oeis.org

1, 1, 3, 6, 15, 23, 53, 94, 203, 404, 855, 1648, 3416, 6662, 13400, 26406, 53038, 105306, 212051, 422162, 849267, 1696864, 3406077, 6807024, 13642099, 27268122, 54576003, 109096436, 218250874, 436243705, 872533347, 1744312748, 3488432736, 6974783481
Offset: 1

Views

Author

Alois P. Heinz, Jun 21 2014

Keywords

Examples

			From _Gus Wiseman_, Nov 25 2019: (Start)
The a(1) = 1 through a(5) = 15 compositions:
  (1)  (2)  (3)    (4)      (5)
            (1,2)  (1,3)    (1,4)
            (2,1)  (3,1)    (2,3)
                   (1,1,2)  (3,2)
                   (1,2,1)  (4,1)
                   (2,1,1)  (1,1,3)
                            (1,2,2)
                            (1,3,1)
                            (2,1,2)
                            (2,2,1)
                            (3,1,1)
                            (1,1,1,2)
                            (1,1,2,1)
                            (1,2,1,1)
                            (2,1,1,1)
(End)
		

Crossrefs

Column k=1 of A242451.
The complement is counted by A240085.

Programs

  • Maple
    b:= proc(n, i, p, k) option remember; `if`(n=0, p!, `if`(i<1, 0,
          add(b(n-i*j, i-1, p+j, k)/j!, j=[0, $max(1, k)..n/i])))
        end:
    a:= n-> b(n$2, 0, 1) -b(n$2, 0, 2):
    seq(a(n), n=1..50);
  • Mathematica
    Table[Length[Select[Join@@Permutations/@IntegerPartitions[n],Min@@Length/@Split[Sort[#]]==1&]],{n,0,10}] (* Gus Wiseman, Nov 25 2019 *)

Formula

a(n) = 2^(n-1) - A240085(n). - Gus Wiseman, Nov 25 2019

A349794 Numbers whose prime signature has an odd term other than the first or last.

Original entry on oeis.org

30, 42, 60, 66, 70, 78, 84, 102, 105, 110, 114, 120, 130, 132, 138, 140, 150, 154, 156, 165, 168, 170, 174, 182, 186, 190, 195, 204, 210, 220, 222, 228, 230, 231, 238, 240, 246, 255, 258, 260, 264, 266, 270, 273, 276, 280, 282, 285, 286, 290, 294, 300, 308
Offset: 1

Views

Author

Gus Wiseman, Dec 06 2021

Keywords

Comments

A number's prime signature (row n of A124010) is the sequence of positive exponents in its prime factorization.
Also numbers whose multiset of prime factors is not weakly alternating, where we define a sequence to be weakly alternating if it is alternately weakly increasing and weakly decreasing, starting with either. This sequence looks at the somewhat degenerate case where no strict decreases are allowed.

Examples

			The terms and their prime indices begin:
   30: {1,2,3}
   42: {1,2,4}
   60: {1,1,2,3}
   66: {1,2,5}
   70: {1,3,4}
   78: {1,2,6}
   84: {1,1,2,4}
  102: {1,2,7}
  105: {2,3,4}
  110: {1,3,5}
  114: {1,2,8}
  120: {1,1,1,2,3}
  130: {1,3,6}
  132: {1,1,2,5}
  138: {1,2,9}
		

Crossrefs

The complement for compositions is A025047, ranked by A345167.
Signatures of this type are counted by A274230, complement A027383.
The strong case is A289553, complement A167171.
The strong case for compositions is A345192, ranked by A345168.
The version for compositions is A349053, ranked by A349057.
These partitions are counted by A349061, complement A349060, strong A349801.
The non-strict case is counted by A349795.
A001250 counts alternating permutations, complement A348615.
A096441 counts weakly alternating partitions if 0 is appended.
A345164 counts alternating permutations of prime indices, weak A349056.
A345170 counts partitions w/ an alternating permutation, ranked by A345172.
A349052 counts weakly alternating compositions.
A349059 counts weakly alternating ordered factorizations, strong A348610.

Programs

  • Mathematica
    Select[Range[100],PrimeNu[#]>1&&!And@@EvenQ/@Take[Last/@FactorInteger[#],{2,-2}]&]

A353391 Number of compositions of n that are empty, a singleton, or whose run-lengths are a subsequence that is already counted.

Original entry on oeis.org

1, 1, 1, 1, 2, 1, 3, 1, 1, 4, 5, 7, 9, 11, 15, 22, 38, 45, 87, 93
Offset: 0

Views

Author

Gus Wiseman, May 15 2022

Keywords

Examples

			The a(9) = 4 through a(14) = 15 compositions (A..E = 10..14):
  (9)       (A)       (B)       (C)       (D)       (E)
  (333)     (2233)    (141122)  (2244)    (161122)  (2255)
  (121122)  (3322)    (221123)  (4422)    (221125)  (5522)
  (221121)  (131122)  (221132)  (151122)  (221134)  (171122)
            (221131)  (221141)  (221124)  (221143)  (221126)
                      (231122)  (221142)  (221152)  (221135)
                      (321122)  (221151)  (221161)  (221153)
                                (241122)  (251122)  (221162)
                                (421122)  (341122)  (221171)
                                          (431122)  (261122)
                                          (521122)  (351122)
                                                    (531122)
                                                    (621122)
                                                    (122121122)
                                                    (221121221)
		

Crossrefs

The non-recursive version is A353390, ranked by A353402.
The non-recursive consecutive version is A353392, ranked by A353432.
The non-recursive reverse version is A353403.
The unordered version is A353426, ranked by A353393 (nonprime A353389).
The consecutive version is A353430.
These compositions are ranked by A353431.
A003242 counts anti-run compositions, ranked by A333489.
A011782 counts compositions.
A329738 counts uniform compositions, partitions A047966.
A114901 counts compositions with no runs of length 1.
A169942 counts Golomb rulers, ranked by A333222.
A325676 counts knapsack compositions, ranked by A333223.
A325705 counts partitions containing all of their distinct multiplicities.
A329739 counts compositions with all distinct run-length.

Programs

  • Mathematica
    yosQ[y_]:=Length[y]<=1||MemberQ[Subsets[y],Length/@Split[y]]&&yosQ[Length/@Split[y]];
    Table[Length[Select[Join@@Permutations/@IntegerPartitions[n],yosQ]],{n,0,15}]

A261041 Number of partitions of subsets of {1,...,n}, where consecutive integers are required to be in different parts.

Original entry on oeis.org

1, 2, 4, 10, 29, 97, 366, 1534, 7050, 35167, 188835, 1084180, 6618472, 42756208, 291120551, 2081922515, 15590248868, 121920095674, 993343650912, 8414029179365, 73953763887277, 673316834487162, 6340176007793060, 61657373569634586, 618445940056365121
Offset: 0

Views

Author

Alois P. Heinz, Aug 09 2015

Keywords

Comments

From Gus Wiseman, Nov 25 2019: (Start)
Conjecture: Also the number of set partitions of {1, ..., n + 1} where, if x and x + 2 belong to the same block, then so does x + 1. For example, the a(0) = 1 through a(3) = 10 set partitions are:
{{1}} {{1,2}} {{1,2,3}} {{1,2,3,4}}
{{1},{2}} {{1},{2,3}} {{1},{2,3,4}}
{{1,2},{3}} {{1,2},{3,4}}
{{1},{2},{3}} {{1,2,3},{4}}
{{1,4},{2,3}}
{{1},{2},{3,4}}
{{1},{2,3},{4}}
{{1,2},{3},{4}}
{{1,4},{2},{3}}
{{1},{2},{3},{4}}
(End)

Examples

			For n=3 the a(3) = 10 partitions are {}, 1, 2, 3, 1|2, 13, 1|3, 2|3, 13|2, 1|2|3.
From _Gus Wiseman_, Nov 25 2019: (Start)
The a(0) = 1 through a(3) = 10 set partitions:
  {}  {}     {}         {}
      {{1}}  {{1}}      {{1}}
             {{2}}      {{2}}
             {{1},{2}}  {{3}}
                        {{1,3}}
                        {{1},{2}}
                        {{1},{3}}
                        {{2},{3}}
                        {{1,3},{2}}
                        {{1},{2},{3}}
(End)
		

Crossrefs

Programs

  • Maple
    g:= proc(n, l, t) option remember; `if`(n=0, 1, add(`if`(l>0
          and j=l, 0, g(n-1, j, `if`(j=t, t+1, t))), j=0..t))
        end:
    a:= n-> g(n, 0, 1):
    seq(a(n), n=0..30);
  • Mathematica
    g[n_, l_, t_] := g[n, l, t] = If[n==0, 1, Sum[If[l>0 && j==l, 0, g[n-1, j, If[j==t, t+1, t]]], {j, 0, t}]]; a[n_] := g[n, 0, 1]; Table[a[n], {n, 0, 30}] (* Jean-François Alcover, Feb 04 2017, translated from Maple *)
    sps[{}]:={{}};sps[set:{i_,_}]:=Join@@Function[s,Prepend[#,s]&/@sps[Complement[set,s]]]/@Cases[Subsets[set],{i,_}];
    Table[Length[Select[Join@@sps/@Subsets[Range[n]],!MemberQ[#,{_,x_,y_,_}/;x+1==y]&]],{n,0,6}] (* Gus Wiseman, Nov 25 2019 *)
  • PARI
    a261041(n) = sum(k=0,n, sum(j=0,k,stirling(k,j,2)) * sum(j=0,(n-k)\2, binomial(k+j-1,j))); \\ Max Alekseyev, Sep 08 2024

Formula

From Max Alekseyev, Sep 08 2024: (Start)
a(n) = Sum_{k=0..n} A000110(k) * Sum_{j=0..[(n-k)/2]} binomial(k+j-1,j).
G.f.: 1/(1-x) * Sum_{k>=0} A000110(k) * (x/(1-x^2))^k. (End)

A353400 Number of integer compositions of n with all run-lengths > 2.

Original entry on oeis.org

1, 0, 0, 1, 1, 1, 2, 1, 2, 4, 4, 5, 11, 11, 14, 27, 29, 37, 61, 72, 97, 147, 181, 246, 368, 470, 632, 914, 1198, 1611, 2286, 3018, 4079, 5709, 7619, 10329, 14333, 19258, 26142, 36069, 48688, 66114, 90800, 122913, 167020, 228735, 310167, 421708, 576499, 782803
Offset: 0

Views

Author

Gus Wiseman, May 15 2022

Keywords

Examples

			The a(7) = 1 through a(12) = 11 compositions:
  1111111   2222       333         22222        1112222       444
            11111111   111222      1111222      2222111       3333
                       222111      2221111      11111222      111333
                       111111111   1111111111   22211111      222222
                                                11111111111   333111
                                                              11112222
                                                              22221111
                                                              111111222
                                                              111222111
                                                              222111111
                                                              111111111111
		

Crossrefs

The = 2 version is A003242 aerated.
The <= 1 version is A003242 ranked by A333489.
The version for parts instead of run-lengths is A078012, both A353428.
The version for partitions is A100405.
The > 1 version is A114901, ranked by A353427.
The <= 2 version is A128695, matching A335464.
A008466 counts compositions with some part > 2.
A011782 counts compositions.
A106356 counts compositions by number of adjacent equal parts.
A274174 counts compositions with equal parts contiguous.
A329738 counts uniform compositions, partitions A047966.
A329739 counts compositions with all distinct run-lengths.

Programs

  • Maple
    b:= proc(n, h) option remember; `if`(n=0, 1, add(
         `if`(i<>h, add(b(n-i*j, i), j=3..n/i), 0), i=1..n/3))
        end:
    a:= n-> b(n, 0):
    seq(a(n), n=0..50);  # Alois P. Heinz, May 17 2022
  • Mathematica
    Table[Length[Select[Join@@Permutations/@ IntegerPartitions[n],!MemberQ[Length/@Split[#],1|2]&]],{n,0,15}]

Extensions

a(21)-a(49) from Alois P. Heinz, May 17 2022

A357185 Numbers k such that the k-th composition in standard order has the same length as the absolute value of its alternating sum.

Original entry on oeis.org

0, 1, 9, 12, 19, 22, 28, 34, 40, 69, 74, 84, 97, 104, 132, 135, 141, 144, 153, 177, 195, 198, 204, 216, 225, 240, 265, 271, 274, 283, 286, 292, 307, 310, 316, 321, 328, 355, 358, 364, 376, 386, 400, 451, 454, 460, 472, 496, 520, 523, 526, 533, 538, 544, 553
Offset: 1

Views

Author

Gus Wiseman, Sep 28 2022

Keywords

Comments

A composition of n is a finite sequence of positive integers summing to n. The k-th composition in standard order (graded reverse-lexicographic, A066099) is obtained by taking the set of positions of 1's in the reversed binary expansion of k, prepending 0, taking first differences, and reversing again. This gives a bijective correspondence between nonnegative integers and integer compositions.
The alternating sum of a sequence (y_1,...,y_k) is Sum_i (-1)^(i-1) y_i.

Examples

			The sequence together with the corresponding compositions begins:
    0: ()
    1: (1)
    9: (3,1)
   12: (1,3)
   19: (3,1,1)
   22: (2,1,2)
   28: (1,1,3)
   34: (4,2)
   40: (2,4)
   69: (4,2,1)
   74: (3,2,2)
   84: (2,2,3)
   97: (1,5,1)
  104: (1,2,4)
  132: (5,3)
  135: (5,1,1,1)
  141: (4,1,2,1)
		

Crossrefs

See link for sequences related to standard compositions.
For sum equal to twice alternating sum we have A348614, counted by A262977.
For product equal to sum we have A335404, counted by A335405.
These compositions are counted by A357183.
This is the absolute value version of A357184, counted by A357183.
A003242 counts anti-run compositions, ranked by A333489.
A011782 counts compositions.
A025047 counts alternating compositions, ranked by A345167.
A032020 counts strict compositions, ranked by A233564.
A124754 gives alternating sums of standard compositions.
A238279 counts compositions by sum and number of maximal runs.
A357136 counts compositions by alternating sum.

Programs

  • Mathematica
    stc[n_]:=Differences[Prepend[Join @@ Position[Reverse[IntegerDigits[n,2]],1],0]]//Reverse;
    ats[y_]:=Sum[(-1)^(i-1)*y[[i]],{i,Length[y]}];
    Select[Range[0,100],Length[stc[#]]==Abs[ats[stc[#]]]&]

A329862 Positive integers whose binary expansion has cuts-resistance 2.

Original entry on oeis.org

3, 4, 6, 9, 11, 12, 13, 18, 19, 20, 22, 25, 26, 37, 38, 41, 43, 44, 45, 50, 51, 52, 53, 74, 75, 76, 77, 82, 83, 84, 86, 89, 90, 101, 102, 105, 106, 149, 150, 153, 154, 165, 166, 169, 171, 172, 173, 178, 179, 180, 181, 202, 203, 204, 205, 210, 211, 212, 213
Offset: 1

Views

Author

Gus Wiseman, Nov 23 2019

Keywords

Comments

For the operation of shortening all runs by 1, cuts-resistance is defined to be the number of applications required to reach an empty word.

Examples

			The sequence of terms together with their binary expansions begins:
   3:      11
   4:     100
   6:     110
   9:    1001
  11:    1011
  12:    1100
  13:    1101
  18:   10010
  19:   10011
  20:   10100
  22:   10110
  25:   11001
  26:   11010
  37:  100101
  38:  100110
  41:  101001
  43:  101011
  44:  101100
  45:  101101
  50:  110010
		

Crossrefs

Positions of 2's in A319416.
Numbers whose binary expansion has cuts-resistance 1 are A000975.
Binary words with cuts-resistance 2 are conjectured to be A027383.
Compositions with cuts-resistance 2 are A329863.
Cuts-resistance of binary expansion without first digit is A319420.
Binary words counted by cuts-resistance are A319421 and A329860.
Compositions counted by cuts-resistance are A329861.

Programs

  • Mathematica
    degdep[q_]:=Length[NestWhileList[Join@@Rest/@Split[#]&,q,Length[#]>0&]]-1;
    Select[Range[100],degdep[IntegerDigits[#,2]]==2&]

A353392 Number of compositions of n whose own run-lengths are a consecutive subsequence.

Original entry on oeis.org

1, 1, 0, 0, 1, 2, 2, 2, 2, 8, 12, 16, 20, 35, 46, 59, 81, 109, 144, 202, 282
Offset: 0

Views

Author

Gus Wiseman, May 15 2022

Keywords

Examples

			The a(0) = 0 through a(10) = 12 compositions (empty columns indicated by dots, 0 is the empty composition):
  0  1  .  .  22  122  1122  11221  21122  333     1333
                  221  2211  12211  22112  22113   2233
                                           22122   3322
                                           31122   3331
                                           121122  22114
                                           122112  41122
                                           211221  122113
                                           221121  131122
                                                   221131
                                                   311221
                                                   1211221
                                                   1221121
		

Crossrefs

The non-consecutive version for partitions is A325702.
The non-consecutive version is A353390, ranked by A353402.
The non-consecutive recursive version is A353391, ranked by A353431.
The non-consecutive reverse version is A353403.
The recursive version is A353430.
These compositions are ranked by A353432.
A003242 counts anti-run compositions, ranked by A333489.
A011782 counts compositions.
A169942 counts Golomb rulers, ranked by A333222.
A325676 counts knapsack compositions, ranked by A333223.
A329738 counts uniform compositions, partitions A047966.
A329739 counts compositions with all distinct run-lengths.

Programs

  • Mathematica
    Table[Length[Select[Join@@Permutations/@IntegerPartitions[n],#=={}||MemberQ[Join@@Table[Take[#,{i,j}],{i,Length[#]},{j,i,Length[#]}],Length/@Split[#]]&]],{n,0,15}]

A353401 Number of integer compositions of n with all prime run-lengths.

Original entry on oeis.org

1, 0, 1, 1, 1, 1, 4, 3, 6, 9, 10, 18, 27, 35, 54, 83, 107, 176, 242, 354, 515, 774, 1070, 1648, 2332, 3429, 4984, 7326, 10521, 15591, 22517, 32908, 48048, 70044, 101903, 149081, 216973, 316289, 461959, 672664, 981356, 1431256, 2086901, 3041577, 4439226, 6467735
Offset: 0

Views

Author

Gus Wiseman, May 15 2022

Keywords

Examples

			The a(0) = 1 through a(9) = 9 compositions (empty column indicated by dot, 0 is the empty composition):
  0   .  11   111   22   11111   33     11122     44       333
                                 222    22111     1133     11133
                                 1122   1111111   3311     33111
                                 2211             11222    111222
                                                  22211    222111
                                                  112211   1111122
                                                           1112211
                                                           1122111
                                                           2211111
		

Crossrefs

The case of runs equal to 2 is A003242 aerated.
The <= 1 version is A003242 ranked by A333489.
The version for parts instead of run-lengths is A023360, both A353429.
The version for partitions is A055923.
The > 1 version is A114901, ranked by A353427.
The <= 2 version is A128695, matching A335464.
The > 2 version is A353400, partitions A100405.
Words with all distinct run-lengths: A032020, A044813, A098859, A130091, A329739, A351013, A351017.
A005811 counts runs in binary expansion.
A008466 counts compositions with some part > 2.
A011782 counts compositions.
A167606 counts compositions with adjacent parts coprime.
A329738 counts uniform compositions, partitions A047966.

Programs

  • Maple
    b:= proc(n, h) option remember; `if`(n=0, 1, add(`if`(i<>h, add(
         `if`(isprime(j), b(n-i*j, i), 0), j=2..n/i), 0), i=1..n/2))
        end:
    a:= n-> b(n, 0):
    seq(a(n), n=0..60);  # Alois P. Heinz, May 18 2022
  • Mathematica
    Table[Length[Select[Join@@Permutations/@IntegerPartitions[n],!MemberQ[Length/@Split[#],_?(!PrimeQ[#]&)]&]],{n,0,15}]

Extensions

a(21)-a(45) from Alois P. Heinz, May 18 2022

A329863 Number of compositions of n with cuts-resistance 2.

Original entry on oeis.org

0, 0, 1, 0, 3, 6, 9, 22, 47, 88, 179, 354, 691, 1344, 2617, 5042, 9709, 18632, 35639, 68010, 129556, 246202, 467188, 885036, 1674211, 3163094, 5969022, 11251676, 21189382, 39867970, 74950464, 140798302, 264313039, 495861874, 929709687, 1742193854, 3263069271, 6108762316
Offset: 0

Views

Author

Gus Wiseman, Nov 23 2019

Keywords

Comments

A composition of n is a finite sequence of positive integers summing to n.
For the operation of shortening all runs by 1, cuts-resistance is defined to be the number of applications required to reach an empty word.

Examples

			The a(2) = 1 through a(7) = 22 compositions (empty column not shown):
  (1,1)  (2,2)    (1,1,3)    (3,3)      (1,1,5)
         (1,1,2)  (1,2,2)    (1,1,4)    (1,3,3)
         (2,1,1)  (2,2,1)    (4,1,1)    (2,2,3)
                  (3,1,1)    (1,1,2,2)  (3,2,2)
                  (1,1,2,1)  (1,1,3,1)  (3,3,1)
                  (1,2,1,1)  (1,2,2,1)  (5,1,1)
                             (1,3,1,1)  (1,1,2,3)
                             (2,1,1,2)  (1,1,3,2)
                             (2,2,1,1)  (1,1,4,1)
                                        (1,4,1,1)
                                        (2,1,1,3)
                                        (2,1,2,2)
                                        (2,2,1,2)
                                        (2,3,1,1)
                                        (3,1,1,2)
                                        (3,2,1,1)
                                        (1,1,2,1,2)
                                        (1,1,2,2,1)
                                        (1,2,1,1,2)
                                        (1,2,2,1,1)
                                        (2,1,1,2,1)
                                        (2,1,2,1,1)
		

Crossrefs

Column k = 2 of A329861.
Compositions with cuts-resistance 1 are A003242.
Compositions with runs-resistance 2 are A329745.
Numbers whose binary expansion has cuts-resistance 2 are A329862.
Binary words with cuts-resistance 2 are conjectured to be A027383.
Cuts-resistance of binary expansion is A319416.
Binary words counted by cuts-resistance are A319421 and A329860.

Programs

  • Mathematica
    degdep[q_]:=Length[NestWhileList[Join@@Rest/@Split[#]&,q,Length[#]>0&]]-1;
    Table[Length[Select[Join@@Permutations/@IntegerPartitions[n],degdep[#]==2&]],{n,0,10}]
  • PARI
    Ca(N) = {1/(1-sum(k=1, N, x^k/(1+x^k)))}
    A_x(N) = {my(x='x+O('x^N)); concat([0,0],Vec(-1+(1+sum(m=1,N, Ca(N)*x^(2*m)*(Ca(N)-1)/(1+x^m*(2+x^m*(1+Ca(N))))))/(1-sum(m=1,N, Ca(N)*x^(2*m)/(1+x^m*(2+x^m*(1+Ca(N))))))))}
    A_x(38) \\ John Tyler Rascoe, Feb 20 2025

Formula

G.f.: -1 + (1 + Ca(x) * Sum_{m>0} x^(2*m) * (Ca(x)-1)/(1 + x^m * (2 + x^m * (1+Ca(x)))))/(1 - Ca(x) * Sum_{m>0} x^(2*m)/(1 + x^m * (2 + x^m * (1+Ca(x))))) where Ca(x) is the g.f. for A003242. - John Tyler Rascoe, Feb 20 2025

Extensions

a(21) onwards from John Tyler Rascoe, Feb 20 2025
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