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.

User: Michael D. Weiner

Michael D. Weiner's wiki page.

Michael D. Weiner has authored 12 sequences. Here are the ten most recent ones:

A372310 Number of permutations of length n avoiding the pattern 1324 and with 1 appearing before n.

Original entry on oeis.org

1, 3, 11, 45, 198, 919, 4446, 22239, 114347, 601722, 3229614, 17632437, 97707195, 548538588, 3115293151, 17875151109, 103511938302, 604392787819, 3555410248782, 21057224371290, 125484804821226, 752020468811244, 4530163818778839, 27419805899781843, 166694596163875206
Offset: 2

Author

Michael D. Weiner, Apr 26 2024

Keywords

Comments

This sequence counts the number of permutations of size n written in one-line notation that avoid the pattern 1324 and have the 1 appearing before the n.

Examples

			For n=4, a(4)=11 is counting the permutations (in one-line notation): 1234, 1243, 1342, 1423, 1432, 2134, 2143, 2314, 3124, 3142, 3214.
		

Crossrefs

Invert of shifted A000139.

Programs

  • Maple
    f:= proc(n) f(n):= 2*(3*n)!/((2*n+1)!*(n+1)!) end:
    a:= proc(n) option remember; `if`(n=1, 1,
          add(a(n-i)*f(i), i=1..n))
        end:
    seq(a(n), n=2..26);  # Alois P. Heinz, Apr 26 2024
  • Mathematica
    a[1] = 1; a[n_] := a[n] = 2*Sum[a[n-k]*(3*k)!/((2*k + 1)!*(k+1)!), {k, 1, n-1}]; Table[a[n], {n, 2, 30}] (* Vaclav Kotesovec, Jul 06 2024 *)

Formula

G.f.: A(x) = (x*(B(x)-2))/(3-B(x)), where B(x) is the g.f. for A000139. (See arxiv paper by Gil, Lopez, Weiner.)
G.f. satisfies 0 = x^4*(8*x-1) + x^2*(9*x-1)*(4*x-1)*A(x) + x*(6*x-1)*(9*x-2)*A(x)^2 + (27*x^2-9*x+1)*A(x)^3.
a(n) ~ 3^(3*n - 9/2) / (sqrt(Pi) * n^(5/2) * 2^(2*n - 5)). - Vaclav Kotesovec, Jul 06 2024
D-finite with recurrence 4*(n-1)*(2*n-5)*a(n) -6*(n-2)*(23*n-63)*a(n-1) +9*(99*n^2-567*n+818)*a(n-2) +81*(-31*n^2+215*n-374)*a(n-3) +243*(3*n-13)*(3*n-14)*a(n-4)=0. - R. J. Mathar, Sep 27 2024

A298358 a(n) is the number of rooted 3-connected bicubic planar maps with 2n vertices.

Original entry on oeis.org

1, 0, 0, 1, 0, 3, 7, 15, 63, 168, 561, 1881, 6110, 21087, 72174, 250775, 883116, 3125910, 11174280, 40209852, 145590720, 530358095, 1941862860, 7144623447, 26403493545, 97971775008, 364903633215, 1363847131450, 5113975285788, 19233646581282
Offset: 1

Author

Michael D. Weiner, Jan 17 2018

Keywords

Examples

			A(x) = x + x^4 + 3*x^6 + 7*x^7 + 15*x^8 + 63*x^9 + 168*x^10 + 561*x^11 + ...
		

Crossrefs

Programs

  • Mathematica
    kmax = 30; b[0] = 1; b[n_] := 3*2^(n - 1)*CatalanNumber[n]/(n + 2);
    G[x_] = Sum[b[k] x^k, {k, 0, kmax}];
    A[_] = 1;
    Do[A[x_] = G[x/(1 + A[x] + O[x]^k)^3] - 1 // Normal, {k, 1, kmax + 1}];
    CoefficientList[A[x], x][[2 ;; -2]] (* Jean-François Alcover, Jun 19 2018 *)
  • PARI
    seq(N) = {
      my(x='x+O('x^(N+2)), y=(1-sqrt(1-8*x))/(4*x), g=(1+4*y-y^2)/4);
      Vec(subst(g-1, 'x, serreverse(x*g^3)));
    };
    seq(30) \\ Gheorghe Coserea, Apr 11 2018

Formula

G.f.: A(x) = G(x/(1+A(x))^3)-1 where A(x*(G(x))^3) = G(x)-1 and G(x) = g.f. for A000257.
From Gheorghe Coserea, Apr 16 2018: (Start)
y = A(x)/x satisfies: 0 = x^6*y^7 + 6*x^5*y^6 + 15*x^4*y^5 + 4*x^3*(5 - 3*x)*y^4 + x^2*(15 - 37*x)*y^3 + x*(16*x^2 - 39*x + 6)*y^2 + (24*x^2 - 15*x + 1)*y + (9*x - 1).
A(x) = serreverse((1+x)^3*(1 + 12*x - (1-4*x)^(3/2))/(2*(4*x+3)^2)); equivalently, it can be rewritten as A(x) = serreverse((y-1)*(y^2+y-1)^3/(y^5*(3*y-2)^2)), where y = A000108(x). (End)
a(n) ~ 3 * 2^(9*n-1) / (sqrt(Pi) * 17^(5/2) * 5^(3*n - 5/2) * n^(5/2)). - Gheorghe Coserea and Vaclav Kotesovec, Apr 16 2018

A274259 Number of factor-free Dyck words with slope 7/3 and length 10n.

Original entry on oeis.org

1, 12, 570, 44689, 4223479, 441010458, 49014411306, 5685822210429, 680500195656621, 83406972284096638, 10416465145620729162, 1320749077779826216029, 169570747575202480367168, 22000830732097549119672094, 2880094468241888675318895339, 379941591968957300338548388051, 50458777676743899501139029335858
Offset: 0

Author

Michael D. Weiner, Jun 16 2016

Keywords

Comments

a(n) is the number of lattice paths (allowing only north and east steps) starting at (0,0) and ending at (3n,7n) that stay below the line y=7/3x and also do not contain a proper subpath of smaller size.

Examples

			a(2) = 570 since there are 570 lattice paths (allowing only north and east steps) starting at (0,0) and ending at (6,14) that stay below the line y=7/3x and also do not contain a proper subpath of small size; e.g., ENNENENNNENNENNNENNN is a factor-free Dyck word but ENNENNENNEENNNNNENNN contains the factor ENNEENNNNN.
		

Crossrefs

Factor-free Dyck words: A005807 (slope 3/2), A274052 (slope 5/2), A274244 (slope 7/2), A274256 (slope 9/2), A274257 (slope 4/3), A274258 (slope 5/3).

Formula

Conjectural o.g.f.: Let E(x) = exp( Sum_{n >= 1} binomial(10*n, 3*n)*x^n/n ). Then A(x) = ( x/series reversion of x*E(x) )^(1/10) = 1 + 12*x + 570*x^2 + 44689*x^3 + ... . Equivalently, [x^n]( A(x)^(10*n) ) = binomial(10*n, 3*n) for n = 0,1,2,... . - Peter Bala, Jan 03 2020

A274258 Number of factor-free Dyck words with slope 5/3 and length 8n.

Original entry on oeis.org

1, 7, 133, 4140, 154938, 6398717, 281086555, 12882897819, 609038885805, 29481041746958, 1453894927584477, 72789271870852237, 3689808842747726368, 189006099916444293090, 9768094831949586349262, 508712466332195692590121, 26670630123516854616641671, 1406503552584980596900001922, 74559627811441047591493767590
Offset: 0

Author

Michael D. Weiner, Jun 16 2016

Keywords

Comments

a(n) is the number of lattice paths (allowing only north and east steps) starting at (0,0) and ending at (3n,5n) that stay below the line y=5/3x and also do not contain a proper subpath of smaller size.

Examples

			a(2) = 133 since there are 133 lattice paths (allowing only north and east steps) starting at (0,0) and ending at (6,10) that stay below the line y=5/3x and also do not contain a proper subpath of small size; e.g., ENEEEENNNNENNNNN is a factor-free Dyck word but ENEENNENNNEENNNN contains the factor EENNENNN.
		

Crossrefs

Factor-free Dyck words: A005807 (slope 3/2), A274052 (slope 5/2), A274244 (slope 7/2), A274256 (slope 9/2), A274257 (slope 4/3), A274259 (slope 7/3).

Formula

Conjectural o.g.f.: Let E(x) = exp( Sum_{n >= 1} binomial(8*n, 3*n)*x^n/n ). Then A(x) = ( x/series reversion of x*E(x) )^(1/8) = 1 + 7*x + 133*x^2 + 4140*x^3 + ... . Equivalently, [x^n]( A(x)^(8*n) ) = binomial(8*n, 3*n) for n = 0,1,2,... . - Peter Bala, Jan 01 2020

A274257 Number of factor-free Dyck words with slope 4/3 and length 7n.

Original entry on oeis.org

1, 5, 52, 880, 17856, 399296, 9491008, 235274240, 6014201600, 157387037696, 4195621863424, 113534211297280, 3110485641494528, 86107512380129280, 2404899661362184192, 67680890349732102144, 1917436905101367443456, 54640222663002565640192, 1565130555077611323392000, 45039415225401829826232320
Offset: 0

Author

Michael D. Weiner, Jun 16 2016

Keywords

Comments

a(n) is the number of lattice paths (allowing only north and east steps) starting at (0,0) and ending at (3n,4n) that stay below the line y=4/3x and also do not contain a proper subpath of smaller size.

Examples

			a(2) = 52 since there are 52 lattice paths (allowing only north and east steps) starting at (0,0) and ending at (6,8) that stay below the line y=4/3x and also do not contain a proper subpath of small size; e.g., EENEENENNENNNN is a factor-free Dyck word but ENEEENNENNENNN contains the factor EENNENN.
		

Crossrefs

Cf. A005807 (slope 3/2), A274052 (slope 5/2), A274244 (slope 7/2), A274256 (slope 9/2), A274258 (slope 5/3), A274259 (slope 7/3).

Programs

  • Mathematica
    m = 20; f[_] = 0;
    Do[f[x_] = (1/(x+1)^4)(-(x^2 (x+1) f[x]^4) + x f[x]^6 + (x-1) x f[x]^5 - (x - 3) x (x+1)^2 f[x]^3 + x (x+1)^3 f[x]^2 + (x+1)^5) + O[x]^m, {m}];
    CoefficientList[f[x], x] (* Jean-François Alcover, Sep 28 2019 *)

Formula

G.f. satisfies: 0 = x*f^6 + x*(x-1)*f^5 - x^2*(x+1)*f^4 - x*(x-3)*(x+1)^2*f^3 + x*(x+1)^3*f^2 - (x+1)^4*f + (x+1)^5. - Michael D. Weiner, Jan 14 2019
Conjectural o.g.f.: Let E(x) = exp( Sum_{n >= 1} binomial(7*n, 3*n)*x^n/n ). Then A(x) = ( x/series reversion of x*E(x) )^(1/7) = 1 + 5*x + 52*x^2 + 880*x^3 + .... Equivalently, [x^n]( A(x)^(7*n) ) = binomial(7*n, 3*n) for n = 0,1,2,.... - Peter Bala, Jan 01 2020

A274256 Number of factor-free Dyck words with slope 9/2 and length 11n.

Original entry on oeis.org

1, 5, 70, 1696, 49493, 1593861, 54591225, 1950653202, 71889214644, 2712628146949, 104277713515456, 4069334248174800, 160785480249706192, 6419443865094494044, 258585021917711797850, 10496205397574996367474, 428899108081734423242550, 17628723180468295514015268, 728347675604866545590505024
Offset: 0

Author

Michael D. Weiner, Jun 16 2016

Keywords

Comments

a(n) is the number of lattice paths (allowing only north and east steps) starting at (0,0) and ending at (2n,9n) that stay below the line y=9/2x and also do not contain a proper subpath of smaller size.

Examples

			a(2) = 70 since there are 70 lattice paths (allowing only north and east steps) starting at (0,0) and ending at (4,18) that stay below the line y=9/2x and also do not contain a proper subpath of small size; e.g., ENNENNENNNNNNENNNNNNNN is a factor-free Dyck word but ENEENENNNNNNNNNNNNNNNN contains the factor ENENNNNNNNN.
		

Crossrefs

Factor-free Dyck words: A005807 (slope 3/2), A274052 (slope 5/2), A274244 (slope 7/2), A274257 (slope 4/3), A274258 (slope 5/3), A274259 (slope 7/3).

Formula

Conjectural o.g.f.: Let E(x) = exp( Sum_{n >= 1} binomial(11*n,2*n)*x^n/n ). Then A(x) = ( x/series reversion of x*E(x) )^(1/11) = 1 + 5*x + 70*x^2 + 1696*x^3 + ... . Equivalently, [x^n]( A(x)^(11*n) ) = binomial(11*n, 2*n) for n = 0,1,2,... . - Peter Bala, Jan 01 2020

A274244 Number of factor-free Dyck words with slope 7/2 and length 9n.

Original entry on oeis.org

1, 4, 34, 494, 8615, 165550, 3380923, 71999763, 1580990725, 35537491360, 813691565184, 18911247654404, 444978958424224, 10579389908116344, 253756528273411250, 6133110915783398175, 149219383150626519874, 3651756292682801022384, 89830021324956206790496, 2219945238901447637080235, 55088272581138888326634644
Offset: 0

Author

Michael D. Weiner, Jun 15 2016

Keywords

Comments

a(n) is the number of lattice paths (allowing only north and east steps) starting at (0,0) and ending at (2n,7n) that stay below the line y=7/2x and also do not contain a proper subpath of smaller size.

Examples

			a(2) = 34 since there are 34 lattice paths (allowing only north and east steps) starting at (0,0) and ending at (4,14) that stay below the line y=7/2x and also do not contain a proper subpath of small size; e.g., EEENNNNENNNNNNNNNN is a factor-free Dyck word but EEENNENNNNNNNNNNNN contains the factor ENNENNNNN.
		

Crossrefs

Factor-free Dyck words: A005807 (slope 3/2), A274052 (slope 5/2), A274256 (slope 9/2), A274257 (slope 4/3), A274259 (slope 7/3).
Cf. A060941.

Formula

Conjectural o.g.f.: Let E(x) = exp( Sum_{n >= 1} binomial(9*n, 2*n)*x^n/n ). Then A(x) = ( x/series reversion of x*E(x) )^(1/9) = 1 + 4*x + 34*x^2 + 494*x^3 + ... . Equivalently, [x^n]( A(x)^(9*n) ) = binomial(9*n, 2*n) for n = 0,1,2,... . - Peter Bala, Jan 01 2020

A274052 Number of factor-free Dyck words with slope 5/2 and length 7n.

Original entry on oeis.org

1, 3, 13, 94, 810, 7667, 76998, 805560, 8684533, 95800850, 1076159466, 12268026894, 141565916433, 1650395185407, 19409211522550, 229984643863260, 2743097412254490, 32907239462485422, 396793477697214450, 4806417317271974580, 58460150525944945840, 713685698665966837135, 8742060290902752902340
Offset: 0

Author

Michael D. Weiner, Jun 08 2016

Keywords

Comments

a(n) is the number of lattice paths (allowing only north and east steps) starting at (0,0) and ending at (2n,5n) that stay below the line y = 5/2x and also do not contain a proper subpath of smaller size.

Examples

			a(2) = 13 since there are 13 lattice paths (allowing only north and east steps) starting at (0,0) and ending at (4,10) that stay below the line y=5/2x and also do not contain a proper subpath of small size; e.g., EEENNNENNNNNNN is a factor-free Dyck word but ENNEENENNNNNNN contains the factor ENENNNN.
		

Crossrefs

Factor-free Dyck words: A005807 (slope 3/2), A274244 (slope 7/2), A274256 (slope 9/2), A274257 (slope 4/3), A274259 (slope 7/3).

Formula

Conjectural o.g.f.: Let E(x) = exp( Sum_{n >= 1} binomial(7*n, 2*n)*x^n/n ). Then A(x) = ( x/series reversion of x*E(x) )^(1/7) = 1 + 3*x + 13*x^2 + 94*x^3 + ... . Equivalently, [x^n]( A(x)^(7*n) ) = binomial(7*n, 2*n) for n = 0,1,2,... . - Peter Bala, Jan 01 2020

A256752 Number of ways to place non-intersecting diagonals in a convex (n+2)-gon so as to create no hexagons.

Original entry on oeis.org

1, 3, 11, 44, 190, 859, 4015, 19248, 94117, 467575, 2353443, 11975568, 61505088, 318406927, 1659801852, 8704865907, 45898065978, 243163198928, 1293769867676, 6910165762943, 37036898772008, 199140325574519, 1073849938338566
Offset: 1

Author

Michael D. Weiner, Apr 09 2015

Keywords

Examples

			a(3)=11 because all 11 dissections of the pentagon are allowed, i.e., the null placement, 5 placements of 1 diagonal and 5 placements of two diagonals.
		

Crossrefs

Programs

  • Mathematica
    Rest[CoefficientList[(InverseSeries[Series[(y-2*y^2+y^5-y^6)/(1-y), {y, 0, 24}], x]-x)/x, x]]

Formula

a(n) = (1/(n+1))*Sum_{i=0..floor(n/4)} Sum_{k=i+1..n-3*i} (-1)^i*binomial(n+k,k)*binomial(k,i)*binomial(n-4*i-1,k-i-1), n !== 0 (mod 4),
a(n) = ((-1)^(n/4)/(n+1))*binomial(5*n/4,n/4) + (1/(n+1))*Sum_{i=0..(n/4)-1} Sum_{k=i+1..n-3*i} (-1)^i*binomial(n+k,k)*binomial(k,i)*binomial(n-4*i-1,k-i-1), n == 0 (mod 4).

A253194 Number of ways to place non-intersecting diagonals in a convex (n+2)-gon so as to create no pentagons.

Original entry on oeis.org

1, 3, 10, 39, 162, 707, 3190, 14766, 69719, 334481, 1625846, 7989908, 39631204, 198151579, 997623275, 5053274850, 25734158411, 131680565544, 676693557574, 3490897656337, 18071699948492, 93851485181749, 488815126122166
Offset: 1

Author

Michael D. Weiner, Mar 24 2015

Keywords

Examples

			a(3)=10 because the pentagon allows all but the null placement, i.e., 5 placements of 1 diagonal and 5 placements of two diagonals.
		

Crossrefs

Programs

  • Mathematica
    Rest[CoefficientList[(InverseSeries[Series[(y-2*y^2+y^4-y^5)/(1-y),{y,0,24}],x]-x)/x,x]]
  • PARI
    A253194(n)=sum(i=0,(n-1)\3,sum(k=i+1,n-2*i, (-1)^i*binomial(n+k,k)*binomial(k,i)*binomial(n-3*i-1,k-i-1)),if(n%3==0,(-1)^(n/3)*binomial(4*n/3,n/3)))/(n+1) \\ M. F. Hasler, Apr 07 2015

Formula

a(n) = (1/(n+1))*Sum_{i=0..floor(n/3)} Sum_{k=i+1..n-2*i} (-1)^i*binomial(n+k,k)*binomial(k,i)*binomial(n-3*i-1,k-i-1), n !== 0 (mod 3),
a(n) = ((-1)^(n/3)/(n+1))*binomial(4*n/3,n/3) + (1/(n+1))*Sum_{i=0..(n/3)-1} Sum_{k=i+1..n-2*i} (-1)^i*binomial(n+k,k)*binomial(k,i)*binomial(n-3*i-1,k-i-1), n == 0 (mod 3).
Recurrence: 275*(n-2)*(n-1)*n*(n+1)*(13962464*n^5 - 196202616*n^4 + 1069508732*n^3 - 2802358002*n^2 + 3480787751*n - 1597000860)*a(n) = 900*(n-2)*(n-1)*n*(27924928*n^6 - 406367696*n^5 + 2336399896*n^4 - 6678345644*n^3 + 9735406192*n^2 - 6526643891*n + 1424056473)*a(n-1) - 8*(n-2)*(n-1)*(1870970176*n^7 - 30033090896*n^6 + 197840216728*n^5 - 682911269612*n^4 + 1297104157966*n^3 - 1273486799084*n^2 + 486871358313*n + 21712608900)*a(n-2) - 16*(n-2)*(2569093376*n^8 - 47662201536*n^7 + 375012676176*n^6 - 1627682459628*n^5 + 4239503473896*n^4 - 6734585440155*n^3 + 6299789310412*n^2 - 3112752665481*n + 598681926090)*a(n-3) + 16*(2457393664*n^9 - 54190809728*n^8 + 518749193184*n^7 - 2816319789288*n^6 + 9492888047100*n^5 - 20388222826734*n^4 + 27407291375141*n^3 - 21462176121217*n^2 + 8117426803296*n - 745665750648)*a(n-4) - 8*(n-4)*(2*n - 7)*(4*n - 17)*(4*n - 11)*(13962464*n^5 - 126390296*n^4 + 424322908*n^3 - 631422862*n^2 + 369599799*n - 31302531)*a(n-5). - Vaclav Kotesovec, Mar 30 2015