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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A335461 Triangle read by rows where T(n,k) is the number of patterns of length n with k runs.

Original entry on oeis.org

1, 0, 1, 0, 1, 2, 0, 1, 4, 8, 0, 1, 6, 24, 44, 0, 1, 8, 48, 176, 308, 0, 1, 10, 80, 440, 1540, 2612, 0, 1, 12, 120, 880, 4620, 15672, 25988, 0, 1, 14, 168, 1540, 10780, 54852, 181916, 296564, 0, 1, 16, 224, 2464, 21560, 146272, 727664, 2372512, 3816548
Offset: 0

Views

Author

Gus Wiseman, Jul 03 2020

Keywords

Comments

We define a pattern to be a finite sequence covering an initial interval of positive integers. Patterns are counted by A000670 and ranked by A333217.

Examples

			Triangle begins:
     1
     0     1
     0     1     2
     0     1     4     8
     0     1     6    24    44
     0     1     8    48   176   308
     0     1    10    80   440  1540  2612
     0     1    12   120   880  4620 15672 25988
Row n = 3 counts the following patterns:
  (1,1,1)  (1,1,2)  (1,2,1)
           (1,2,2)  (1,2,3)
           (2,1,1)  (1,3,2)
           (2,2,1)  (2,1,2)
                    (2,1,3)
                    (2,3,1)
                    (3,1,2)
                    (3,2,1)
		

Crossrefs

Row sums are A000670.
Column n = k is A005649 (anti-run patterns).
Central coefficients are A337564.
The version for compositions is A333755.
Runs of standard compositions are counted by A124767.
Run-lengths of standard compositions are A333769.

Programs

  • Mathematica
    allnorm[n_]:=If[n<=0,{{}},Function[s,Array[Count[s,y_/;y<=#]+1&,n]]/@Subsets[Range[n-1]+1]];
    Table[Length[Select[Join@@Permutations/@allnorm[n],Length[Split[#]]==k&]],{n,0,5},{k,0,n}]
  • PARI
    \\ here b(n) is A005649.
    b(n) = {sum(k=0, n, stirling(n,k,2)*(k + 1)!)}
    T(n,k)=if(n==0, k==0, b(k-1)*binomial(n-1,k-1)) \\ Andrew Howroyd, Dec 31 2020

Formula

T(n,k) = A005649(k-1) * binomial(n-1,k-1) for k > 0. - Andrew Howroyd, Dec 31 2020

A330150 Expansion of e.g.f. exp(-x) / (1 - log(1 + x)).

Original entry on oeis.org

1, 0, 0, 1, -1, 8, -16, 159, -659, 6824, -46680, 517581, -4941685, 61043344, -735256328, 10269016939, -147207286503, 2322683458544, -38298239486672, 677630804946393, -12581447014620585, 247342217288517496, -5096876494438056928, 110338442309322274295
Offset: 0

Views

Author

Ilya Gutkovskiy, Dec 03 2019

Keywords

Comments

Inverse binomial transform of A006252.

Crossrefs

Programs

  • Mathematica
    nmax = 23; CoefficientList[Series[Exp[-x]/(1 - Log[1 + x]), {x, 0, nmax}], x] Range[0, nmax]!

Formula

a(n) = Sum_{k=0..n} (-1)^(n - k) * binomial(n,k) * A006252(k).
a(n) = (-1)^n + Sum_{k=1..n} (-1)^(k-1) * (k-1)! * binomial(n,k) * a(n-k). - Seiichi Manyama, Dec 19 2023

A337506 Triangle read by rows where T(n,k) is the number of length-n sequences covering an initial interval of positive integers with k maximal anti-runs.

Original entry on oeis.org

1, 0, 1, 0, 2, 1, 0, 8, 4, 1, 0, 44, 24, 6, 1, 0, 308, 176, 48, 8, 1, 0, 2612, 1540, 440, 80, 10, 1, 0, 25988, 15672, 4620, 880, 120, 12, 1, 0, 296564, 181916, 54852, 10780, 1540, 168, 14, 1, 0, 3816548, 2372512, 727664, 146272, 21560, 2464, 224, 16, 1
Offset: 0

Views

Author

Gus Wiseman, Sep 06 2020

Keywords

Comments

An anti-run is a sequence with no adjacent equal parts. The number of maximal anti-runs is one more than the number of adjacent equal parts.

Examples

			Triangle begins:
  1
  0      1
  0      2      1
  0      8      4      1
  0     44     24      6      1
  0    308    176     48      8      1
  0   2612   1540    440     80     10      1
  0  25988  15672   4620    880    120     12      1
  0 296564 181916  54852  10780   1540    168     14      1
Row n = 3 counts the following sequences (empty column indicated by dot):
  .  (1,2,1)  (1,1,2)  (1,1,1)
     (1,2,3)  (1,2,2)
     (1,3,2)  (2,1,1)
     (2,1,2)  (2,2,1)
     (2,1,3)
     (2,3,1)
     (3,1,2)
     (3,2,1)
		

Crossrefs

A000670 gives row sums.
A005649 gives column k = 1.
A337507 gives column k = 2.
A337505 gives the diagonal n = 2*k.
A106356 is the version for compositions.
A238130/A238279/A333755 is the version for runs in compositions.
A335461 has the reversed rows (except zeros).
A003242 counts anti-run compositions.
A124762 counts adjacent equal terms in standard compositions.
A124767 counts maximal runs in standard compositions.
A333381 counts maximal anti-runs in standard compositions.
A333382 counts adjacent unequal terms in standard compositions.
A333489 ranks anti-run compositions.
A333769 gives maximal run-lengths in standard compositions.
A337565 gives maximal anti-run lengths in standard compositions.

Programs

  • Mathematica
    allnorm[n_]:=If[n<=0,{{}},Function[s,Array[Count[s,y_/;y<=#]+1&,n]]/@Subsets[Range[n-1]+1]];
    Table[Length[Select[Join@@Permutations/@allnorm[n],Length[Split[#,UnsameQ]]==k&]],{n,0,5},{k,0,n}]
  • PARI
    \\ here b(n) is A005649.
    b(n) = {sum(k=0, n, stirling(n,k,2)*(k + 1)!)}
    T(n,k)=if(n==0, k==0, b(n-k)*binomial(n-1,k-1)) \\ Andrew Howroyd, Dec 31 2020

Formula

T(n,k) = A005649(n-k) * binomial(n-1,k-1) for k > 0. - Andrew Howroyd, Dec 31 2020

Extensions

Terms a(45) and beyond from Andrew Howroyd, Dec 31 2020

A306416 Number of ordered 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, 2, 0, 26, 84, 950, 6000, 62522, 556116, 6259598, 69319848, 874356338, 11384093196, 161462123894, 2397736692144, 37994808171962, 631767062124564, 11088109048500158, 203828700127054008, 3928762035148317314, 79079452776283889820, 1661265965479375937030, 36332908076071038467520, 826376466514358722894154
Offset: 0

Views

Author

Gus Wiseman, Feb 14 2019

Keywords

Examples

			The a(4) = 2 ordered set partitions are: {{1,3},{2,4}}, {{2,4},{1,3}}.
		

Crossrefs

Cf. A000110, A000126, A000296, A000670, A001610, A032032 (adjacencies allowed), A052841 (singletons allowed), A124323, A169985, A306417, A324011 (orderless case), A324012, A324015.

Programs

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

Extensions

a(12)-a(26) from Alois P. Heinz, Feb 14 2019

A357868 Square array T(n,k), n >= 0, k >= 0, read by antidiagonals downwards, where T(n,k) = Sum_{j=0..n} (k*j)!* Stirling2(n,k*j).

Original entry on oeis.org

1, 1, 0, 1, 1, 0, 1, 0, 3, 0, 1, 0, 2, 13, 0, 1, 0, 0, 6, 75, 0, 1, 0, 0, 6, 38, 541, 0, 1, 0, 0, 0, 36, 270, 4683, 0, 1, 0, 0, 0, 24, 150, 2342, 47293, 0, 1, 0, 0, 0, 0, 240, 1260, 23646, 545835, 0, 1, 0, 0, 0, 0, 120, 1560, 16926, 272918, 7087261, 0, 1, 0, 0, 0, 0, 0, 1800, 8400, 197316, 3543630, 102247563, 0
Offset: 0

Views

Author

Seiichi Manyama, Oct 17 2022

Keywords

Examples

			Square array begins:
  1,   1,   1,   1,   1,   1, ...
  0,   1,   0,   0,   0,   0, ...
  0,   3,   2,   0,   0,   0, ...
  0,  13,   6,   6,   0,   0, ...
  0,  75,  38,  36,  24,   0, ...
  0, 541, 270, 150, 240, 120, ...
		

Crossrefs

Programs

  • PARI
    T(n, k) = sum(j=0, n, (k*j)!*stirling(n, k*j, 2));
    
  • PARI
    T(n, k) = if(k==0, 0^n, n!*polcoef(1/(1-(exp(x+x*O(x^n))-1)^k), n));

Formula

For k > 0, e.g.f. of column k: 1/(1 - (exp(x) - 1)^k).
T(0,k) = 1; T(n,k) = k! * Sum_{j=1..n} binomial(n,j) * Stirling2(j,k) * T(n-j,k).

A363732 Triangle read by rows. The triangle algorithm applied to (-1)^n/n!.

Original entry on oeis.org

1, -2, 1, 5, -4, 1, -15, 15, -6, 1, 52, -60, 30, -8, 1, -203, 260, -150, 50, -10, 1, 877, -1218, 780, -300, 75, -12, 1, -4140, 6139, -4263, 1820, -525, 105, -14, 1, 21147, -33120, 24556, -11368, 3640, -840, 140, -16, 1, -115975, 190323, -149040, 73668, -25578, 6552, -1260, 180, -18, 1
Offset: 0

Views

Author

Peter Luschny, Jun 18 2023

Keywords

Comments

The triangle algorithm, as understood here, is a transformation that maps a sequence of integers (a(n) : n >= 0) to a polynomial sequence. A polynomial sequence is a sequence of polynomials (P(n,x) : n >= 0) with degree(P(n, x)) = n for all n >= 0.
The polynomials P(n, x) are recursively defined by P(n, x) = p(n, 0, x), where the initial sequence is p(0, m, x) = a(m), and for n > 0 is given by
p(n, m, x) = (m + 1)*p(n - 1, m + 1, x) - (m + 1 - x)*p(n - 1, m, x).
Here we identify the polynomial sequence with the infinite lower triangular array of its coefficients, T(n, k) = [x^k] P(n, x). We call the mapping (a(n) : n >= 0) -> (T(n, k) : 0 <= k <= n) the 'triangle algorithm', following the lead of Kawasaki and Ohno.
Evaluating P(n, x) at different values of x gives rise to a multitude of other sequences; in particular, the transformation a(n) -> b(n) = P(n, 1) will be called the Akiyama-Tanigawa transform of a.
The triangle algorithm was studied by Akiyama and Tanigawa, Chen, Imatomi, Arakawa and Kaneko, Kawasaki and Ohno, and others, at first in connection with the Bernoulli and Poly-Bernoulli numbers.
.
The paradigmatic examples are:
a(n) = 1 -> x^n, the standard base of polynomials, A023531.
a(n) = n + 1 -> binomial(n, k), Pascal triangle, A007318.
a(n) = n + 1 -> P(n, 1) powers of 2, A000079.
a(n) = n + 1 -> P(n, 0) the all 1's sequence A000012.
a(n) = 2^n -> [x^k] P(n, x), A154921.
a(n) = 2^n -> P(n, 0) Fubini numbers, A000670.
a(n) = 2^n -> P(n, 1) ordered set partitions of subsets of [n], A000629.
a(n) = 2^n -> P(n,-1) osp. of [n] with even number of blocks, A052841.
a(n) = 1 / (n + 1) -> [x^k] B(n, x), Bernoulli polynomials, A196838/A196839.
a(n) = 1 / (n + 1) -> B(n, 1), the Bernoulli numbers, A164555/A027642.
a(n) = Chen(n) -> skp(n, x), Swiss-Knife polynomials, A153641.
a(n) = Chen(n) -> P(n, 0), 2^n*Euler(n, 1/2) = Euler(n), A122045.
a(n) = Chen(n) -> P(n, 1), 2^n*Euler(n, 1), A155585.
a(n) = (-1)^n/n! -> [x^k] P(n, x) this "Bell" triangle.
a(n) = (-1)^n/n! -> (-1)^n*P(n, 1) = Bell(n), A000110.
a(n) = (-1)^n/n! -> (-1)^n*P(n,-1) = 2-Bell(n), A005493.
a(n) = 1/n! -> (-1)^n*P(n, 1) = complementary Bell(n), A000587.
a(n) = 1/n! -> (-1)^n*P(n,-1) = complementary 2-Bell(n), A074051.
(For Chen's sequence see A363524.)
.
The present sequence deals with the case of the Bell numbers. In contrast to Aitken's array A011971 and its variants A123346 and A011972, the Bell numbers do not appear as a column of the triangle but as row sums (times (-1)^n), i.e., as values of the associated polynomials at x = 1. Comparing this with a similar situation with the Bernoulli numbers/polynomials, our triangle could be viewed as a more organic generalization of the Bell numbers. Indeed, the names 'Bell triangle' and 'Bell polynomials' would be justified here; but these are already assigned to other concepts.

Examples

			The triangle T(n, k) starts:
  [0]     1;
  [1]    -2,      1;
  [2]     5,     -4,     1;
  [3]   -15,     15,    -6,      1;
  [4]    52,    -60,    30,     -8,    1;
  [5]  -203,    260,  -150,     50,  -10,    1;
  [6]   877,  -1218,   780,   -300,   75,  -12,   1;
  [7] -4140,   6139, -4263,   1820, -525,  105, -14,   1;
  [8] 21147, -33120, 24556, -11368, 3640, -840, 140, -16, 1;
		

Crossrefs

Cf. A293037 (row sums), A000110 (row sums, unsigned), A005493 (alternating row sums, signed).

Programs

  • Maple
    TA := proc(a, n, m, x) option remember; if n = 0 then a(m) else
    normal((m + 1)*TA(a, n - 1, m + 1, x) - (m + 1 - x)*TA(a, n - 1, m, x)) fi end:
    seq(seq(coeff(TA(n -> (-1)^n/n!, n, 0, x), x, k), k = 0..n), n = 0..10);
  • Mathematica
    (* rows[0..n], n[0..oo] *)
    (* row[n]= *)
    n=9;r={};For[a=n+1,a>0,a--,AppendTo[r,(-1)^(a+1)*Sum[StirlingS2[a,k],{k,0,a}]*Product[(2*(a+j))/(2*j+2),{j,0,n-a}]]];r
    (* columns[1..n], n[0..oo] *)
    (* column[n]= *)
    n=0;c={};For[a=1,a<15,a++,AppendTo[c,(-1)^(a+1)*Sum[StirlingS2[a,k],{k,0,a}]*Product[(2*(a+j-1))/(2*j),{j,1,n}]]];c
    (* sequence *)
    s={};For[n=0,n<15,n++,For[a=n+1,a>0,a--,AppendTo[s,(-1)^(a+1)*Sum[StirlingS2[a,k],{k,0,a}]*Product[(2*(a+j))/(2*j+2),{j,0,n-a}]]]];s
    (* Detlef Meya, Jun 22 2023 *)
  • SageMath
    def a(n): return (-1)^n / factorial(n)
    @cached_function
    def p(n, m):
        R = PolynomialRing(QQ, "x")
        if n == 0: return R(a(m))
        return R((m + 1)*p(n - 1, m + 1) - (m + 1 - x)*p(n - 1, m))
    for n in range(10): print(p(n, 0).list())

A052657 Expansion of e.g.f. x^2/((1-x)^2*(1+x)).

Original entry on oeis.org

0, 0, 2, 6, 48, 240, 2160, 15120, 161280, 1451520, 18144000, 199584000, 2874009600, 37362124800, 610248038400, 9153720576000, 167382319104000, 2845499424768000, 57621363351552000, 1094805903679488000, 24329020081766400000, 510909421717094400000, 12364008005553684480000
Offset: 0

Views

Author

encyclopedia(AT)pommard.inria.fr, Jan 25 2000

Keywords

Comments

Stirling transform of -(-1)^n*a(n-1) = [0, 0, 2, -6, 48, -240, ...] is A052841(n-1) = [0, 0, 2, 6, 38, 270, ...]. - Michael Somos, Mar 04 2004

Crossrefs

Programs

  • Maple
    spec := [S,{S=Prod(Z,Z,Sequence(Z),Sequence(Prod(Z,Z)))},labeled]: seq(combstruct[count](spec,size=n), n=0..20);
  • Mathematica
    a[n_] := Floor[n/2] * n!; Array[a, 25, 0] (* Amiram Eldar, Jan 22 2023 *)
  • PARI
    a(n)=if(n<0,0,n!*polcoeff(x^2/(1-x)/(1-x^2)+x*O(x^n),n))
    
  • PARI
    a(n)=n!*(n\2); \\ Joerg Arndt, Jan 22 2023

Formula

a(0)=0, a(1)=0, a(2)=2, n*a(n+2) = (n+2)*a(n+1) + (n^3 + 4*n^2 + 5*n + 2)*a(n).
a(n) = (2*n-1+(-1)^n)*n!/4 = n!*floor(n/2) = n!*A004526(n).
E.g.f.: x^2/((1-x)*(1-x^2)).
Sum_{n>=2} 1/a(n) = 4*CoshIntegral(1) - 4*gamma - 2*sinh(1) + 2 = 4*A099284 - 4*A001620 - 2*A073742 + 2. - Amiram Eldar, Jan 22 2023

A330604 a(n) = Sum_{k>=0} (n*k - 1)^n / 2^(k + 1).

Original entry on oeis.org

1, 0, 9, 278, 16145, 1471774, 194652577, 35275961958, 8397548586177, 2542220603893358, 954003495852753401, 434683708245705663766, 236409592518584290327249, 151286889086525353482149022, 112534788142976814403622739921, 96285847680519841273313314779974
Offset: 0

Views

Author

Ilya Gutkovskiy, Dec 19 2019

Keywords

Crossrefs

Programs

  • Mathematica
    Table[Sum[(n k - 1)^n/2^(k + 1), {k, 0, Infinity}], {n, 0, 15}]
    Join[{1}, Table[n^n HurwitzLerchPhi[1/2, -n, -1/n]/2, {n, 1, 15}]]
    Table[n! SeriesCoefficient[Exp[-x]/(2 - Exp[n x]), {x, 0, n}], {n, 0, 15}]

Formula

a(n) = n! * [x^n] exp(-x) / (2 - exp(n*x)).
a(n) = Sum_{k=0..n} (-1)^(n - k) * binomial(n,k) * n^k * A000670(k).
a(n) ~ n^n * n! / (2 * (log(2))^(n+1)). - Vaclav Kotesovec, Dec 19 2019

A337507 Number of length-n sequences covering an initial interval of positive integers with exactly two maximal anti-runs, or with one pair of adjacent equal parts.

Original entry on oeis.org

0, 0, 1, 4, 24, 176, 1540, 15672, 181916, 2372512, 34348932, 546674120, 9486840748, 178285201008, 3607174453844, 78177409231768, 1806934004612220, 44367502983673664, 1153334584544496676, 31643148872573831016
Offset: 0

Views

Author

Gus Wiseman, Sep 06 2020

Keywords

Comments

An anti-run is a sequence with no adjacent equal parts. For example, the maximal anti-runs in (3,1,1,2,2,2,1) are ((3,1),(1,2),(2),(2,1)). In general, there is one more maximal anti-run than the number of pairs of adjacent equal parts.

Examples

			The a(4) = 24 sequences:
  (2,1,2,2)  (2,1,3,3)  (3,1,2,2)
  (2,2,1,2)  (2,3,3,1)  (3,2,2,1)
  (1,2,2,1)  (3,3,1,2)  (1,1,2,3)
  (2,1,1,2)  (3,3,2,1)  (1,1,3,2)
  (1,1,2,1)  (1,2,2,3)  (2,1,1,3)
  (1,2,1,1)  (1,3,2,2)  (2,3,1,1)
  (1,2,3,3)  (2,2,1,3)  (3,1,1,2)
  (1,3,3,2)  (2,2,3,1)  (3,2,1,1)
		

Crossrefs

A002133 is the version for runs in partitions.
A106357 is the version for compositions.
A337506 has this as column k = 2.
A000670 counts patterns.
A005649 counts anti-run patterns.
A003242 counts anti-run compositions.
A106356 counts compositions by number of maximal anti-runs.
A124762 counts adjacent equal terms in standard compositions.
A124767 counts maximal runs in standard compositions.
A238130/A238279/A333755 count maximal runs in compositions.
A333381 counts maximal anti-runs in standard compositions.
A333382 counts adjacent unequal terms in standard compositions.
A333489 ranks anti-run compositions.
A333769 gives maximal run lengths in standard compositions.
A337565 gives maximal anti-run lengths in standard compositions.

Programs

  • Mathematica
    kv=2;
    allnorm[n_]:=If[n<=0,{{}},Function[s,Array[Count[s,y_/;y<=#]+1&,n]]/@Subsets[Range[n-1]+1]];
    Table[Length[Select[Join@@Permutations/@allnorm[n],Length[Split[#,UnsameQ]]==kv&]],{n,0,6}]

Formula

a(n > 0) = (n - 1)*A005649(n - 2).

A340837 a(n) = (1/2) * Sum_{k>=0} (k*(k - 1))^n / 2^k.

Original entry on oeis.org

1, 2, 52, 3272, 382672, 71819552, 19755648832, 7489898916992, 3743721038908672, 2385494267756237312, 1887436919680269939712, 1815491288416066631616512, 2086364959404184854563049472, 2823211429546048668686123343872, 4443155724532239407325655263035392
Offset: 0

Views

Author

Ilya Gutkovskiy, Jan 23 2021

Keywords

Crossrefs

Programs

  • Mathematica
    Table[(1/2) Sum[(k (k - 1))^n/2^k, {k, 0, Infinity}], {n, 0, 14}]
    Table[(1/2) Sum[(-1)^k Binomial[n, k] HurwitzLerchPhi[1/2, k - 2 n, 0], {k, 0, n}], {n, 0, 14}]

Formula

a(n) = Sum_{k=0..n} (-1)^k * binomial(n,k) * A000670(2*n-k).
a(n) = 2 * A080163(n) for n > 0. - Hugo Pfoertner, Jan 23 2021
a(n) = A122101(2*n,n). - Alois P. Heinz, Jun 23 2023
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