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 1-8 of 8 results.

A117158 Number of permutations avoiding the consecutive pattern 1234.

Original entry on oeis.org

1, 1, 2, 6, 23, 111, 642, 4326, 33333, 288901, 2782082, 29471046, 340568843, 4263603891, 57482264322, 830335952166, 12793889924553, 209449977967081, 3630626729775362, 66429958806679686, 1279448352687538463, 25874432578888440471, 548178875969847203202
Offset: 0

Views

Author

Steven Finch, Apr 26 2006

Keywords

Comments

a(n) is the number of permutations on [n] that avoid the consecutive pattern 1234. It is the same as the number of permutations which avoid 4321.

References

  • F. N. David and D. E. Barton, Combinatorial Chance, Hafner, New York, 1962, pages 156-157.

Crossrefs

Programs

  • Maple
    b:= proc(u, o, t) option remember; `if`(u+o=0, 1,
          `if`(t<2, add(b(u+j-1, o-j, t+1), j=1..o), 0)+
          add(b(u-j, o+j-1, 0), j=1..u))
        end:
    a:= n-> b(n, 0, 0):
    seq(a(n), n=0..30);  # Alois P. Heinz, Oct 07 2013
  • Mathematica
    a[n_]:=Coefficient[Series[2/(Cos[x]-Sin[x]+Exp[ -x]),{x,0,30}],x^n]*n!
    (* second program: *)
    b[u_, o_, t_] := b[u, o, t] = If[u+o==0, 1, If[t<2, Sum[b[u+j-1, o-j, t+1], {j, 1, o}], 0] + Sum[b[u-j, o+j-1, 0], {j, 1, u}]]; a[n_] := b[n, 0, 0]; Table[a[n], {n, 0, 30}] (* Jean-François Alcover, Nov 23 2015, after Alois P. Heinz *)

Formula

From Sergei N. Gladkovskii, Nov 30 2011: (Start)
E.g.f.: 2/(exp(-x) + cos(x) - sin(x)) = 1/W(0) with continued fraction
W(k) = 1 + (x^(2*k))/(f + f*x/(4*k + 1 - x - (4*k + 1)*b/R)), where R := x^(2*k) + b -(x^(4*k+1))/(c + (x^(2*k+1)) + x*c/T); T := 4*k + 3 - x - (4*k + 3)*d/(d +(x^(2*k+1))/W(k+1)), and
f := (4*k)!/(2*k)!; b := (4*k + 1)!/(2*k + 1)!; c := (4*k + 2)!/(2*k + 1)!; and d :=(4*k + 3)!/(2*k + 2)!. (End)
a(n) ~ n! / (sin(r)*r^(n+1)), where r = 1.0384156372665563... is the root of the equation exp(-r) + cos(r) = sin(r). - Vaclav Kotesovec, Dec 11 2013

A117156 Number of permutations avoiding the consecutive pattern 1342.

Original entry on oeis.org

1, 1, 2, 6, 23, 110, 630, 4210, 32150, 276210, 2636720, 27687440, 317169270, 3936056080, 52603684760, 753241509900, 11504852242400, 186705357825800, 3208160592252000, 58188413286031600, 1110946958902609400
Offset: 0

Views

Author

Steven Finch, Apr 26 2006

Keywords

Comments

a(n) is the number of permutations on [n] that avoid the consecutive pattern 1342. It is the same as the number of permutations which avoid 2431, 4213, 3124, 1432, 2341, 4123 or 3214.

References

  • Sergi Elizalde, Asymptotic enumeration of permutations avoiding generalized patterns, Adv. Appl. Math. 36 (2006) 138-155.
  • Sergi Elizalde and Marc Noy, Consecutive patterns in permutations, Adv. Appl. Math. 30 (2003) 110-125.

Crossrefs

Programs

  • Mathematica
    a[n_]:=Coefficient[Series[1/(1-Integrate[Exp[ -t^3/6],{t,0,x}]),{x,0,30}],x^n]*n!
    (* Second program: *)
    m = 21; gf = 1/(1-Sum[If[Mod[k, 3] == 0, (-1)^Mod[k, 6]/(6^(k/3)*(k/3)!), 0]* (x^(k+1)/(k+1)), {k, 0, m}]);
    CoefficientList[gf + O[x]^m, x]*Range[0, m-1]! (* Jean-François Alcover, May 11 2019 *)

Formula

a(n) ~ c * d^n * n!, where d = 1/r = 0.9546118344740519430556804334164431663486451742931588346372174751881329..., where r = 1.04754620033697244977759528695194261... is the root of the equation integral_{x,0,r} exp(-x^3/6) dx = 1, and c = 1.1561985648406071020520797542907648300587978482957199521032311960968187467... . - Vaclav Kotesovec, Aug 23 2014

A264173 Number T(n,k) of permutations of [n] with exactly k (possibly overlapping) occurrences of the consecutive pattern 1324; triangle T(n,k), n>=0, 0<=k<=max(0,floor(n/2-1)), read by rows.

Original entry on oeis.org

1, 1, 2, 6, 23, 1, 110, 10, 632, 86, 2, 4229, 782, 29, 32337, 7571, 407, 5, 278204, 78726, 5856, 94, 2659223, 882997, 84351, 2215, 14, 27959880, 10657118, 1251246, 48234, 322, 320706444, 137977980, 19318314, 984498, 14322, 42, 3985116699, 1910131680, 311306106
Offset: 0

Views

Author

Alois P. Heinz, Nov 06 2015

Keywords

Comments

Pattern 4231 gives the same triangle.

Examples

			T(4,1) = 1: 1324.
T(6,2) = 2: 132546, 142536.
T(8,3) = 5: 13254768, 13264758, 14253768, 14263758, 15263748.
T(10,4) = 14: 132547698(10), 132548697(10), 132647598(10), 132648597(10), 132748596(10), 142537698(10), 142538697(10), 142637598(10), 142638597(10), 142738596(10), 152637498(10), 152638497(10), 152738496(10), 162738495(10).
Triangle T(n,k) begins:
00 :        1;
01 :        1;
02 :        2;
03 :        6;
04 :       23,      1;
05 :      110,     10;
06 :      632,     86,     2;
07 :     4229,    782,    29;
08 :    32337,   7571,   407,    5;
09 :   278204,  78726,  5856,   94;
10 :  2659223, 882997, 84351, 2215, 14;
		

Crossrefs

Row sums give A000142.
T(2n+2,n) gives A000108(n) for n>0.
Cf. A004526, A061206, A264319 (pattern 3412).

Programs

  • Maple
    b:= proc(u, o, t) option remember; expand(`if`(u+o=0, 1,
          add(b(u-j, o+j-1, `if`(t>0 and j (p-> seq(coeff(p, x, i), i=0..degree(p)))(b(n, 0$2)):
    seq(T(n), n=0..14);
  • Mathematica
    b[u_, o_, t_] := b[u, o, t] = Expand[If[u + o == 0, 1, Sum[b[u - j, o + j - 1, If[t > 0 && j < t, -j, 0]], {j, 1, u}] + Sum[b[u + j - 1, o - j, j] * If[t < 0 && -j <= t, x, 1], {j, 1, o}]]];
    T[n_] := Function[p, Table[Coefficient[p, x, i], {i, 0, Exponent[p, x]}]][ b[n, 0, 0]];
    Table[T[n], {n, 0, 14}] // Flatten (* Jean-François Alcover, Apr 30 2017, translated from Maple *)

Formula

Sum_{k>0} k * T(n,k) = ceiling((n-3)*n!/4!) = A061206(n-3) (for n>3).

A117226 Number of permutations of [n] avoiding the consecutive pattern 1243.

Original entry on oeis.org

1, 1, 2, 6, 23, 110, 630, 4204, 32054, 274914, 2619692, 27459344, 313990182, 3889585408, 51888955808, 741668212080, 11307669002720, 183174676857608, 3141820432768752, 56882461258572976, 1084056190235653304, 21692744773505849952, 454758269790599361968
Offset: 0

Views

Author

Steven Finch, Apr 26 2006

Keywords

Comments

a(n) is the number of permutations on [n] that avoid the consecutive pattern 1243. It is the same as the number of permutations which avoid 3421, 4312 or 2134.

Crossrefs

Programs

  • Maple
    b:= proc(u, o, t) option remember; `if`(u+o=0, 1,
          add(b(u-j, o+j-1, 0), j=`if`(t<0, -t, 1)..u)+
          add(b(u+j-1, o-j, `if`(t=0, j, -j)), j=1..o))
        end:
    a:= n-> b(n, 0$2):
    seq(a(n), n=0..25);  # Alois P. Heinz, Nov 07 2013
  • Mathematica
    A[x_]:=Integrate[AiryAi[ -t],{t,0,x}]; B[x_]:=Integrate[AiryBi[ -t],{t,0,x}];
    c=-3^(2/3)*Gamma[2/3]/2; d=-3^(1/6)*Gamma[2/3]/2;
    a[n_]:=SeriesCoefficient[1/(c*A[x]+d*B[x]+1),{x,0,n}]*n!; Table[a[n],{n,0,10}] (* fixed by Vaclav Kotesovec, Aug 23 2014 *)
    (* constant d: *) 1/x/.FindRoot[3^(2/3)*Gamma[2/3]/2 * Integrate[AiryAi[-t],{t,0,x}] + 3^(1/6)*Gamma[2/3]/2 * Integrate[AiryBi[-t],{t,0,x}]==1,{x,1},WorkingPrecision->50] (* Vaclav Kotesovec, Aug 23 2014 *)

Formula

a(n) ~ c * d^n * n!, where d = 0.952891423325053197208702817349165942637814..., c = 1.169657787464830219717093446929792145316... . - Vaclav Kotesovec, Aug 23 2014
From Petros Hadjicostas, Nov 01 2019: (Start)
E.g.f.: 1/W(z), where W(z) := 1 + Sum_{n >= 0} (-1)^(n+1)* z^(3*n+1)/(b(n)*(3*n+1)) with b(n) = A176730(n) = (3*n)!/(3^n*(1/3)_n). (Here (x)_n = x*(x + 1)*...*(x + n - 1) is the Pochhammer symbol, or rising factorial, which is denoted by (x)^n in some papers and books.) The function W(z) satisfies the o.d.e. W'''(z) + z*W'(z) = 0 with W(0) = 1, W'(0) = -1, and W''(0) = 0. [See Theorem 4.3 (Case 1243 with u = 0) in Elizalde and Noy (2003).]
a(n) = Sum_{m = 0..floor((n-1)/3)} (-3)^m * (1/3)_m * binomial(n, 3*m+1) * a(n-3*m-1) for n >= 1 with a(0) = 1. (End)

A113229 Number of permutations avoiding the consecutive pattern 3412.

Original entry on oeis.org

1, 1, 2, 6, 23, 110, 631, 4223, 32301, 277962, 2657797, 27954521, 320752991, 3987045780, 53372351265, 765499019221, 11711207065229, 190365226548070, 3276401870322033, 59523410471007913, 1138295039078030599, 22856576346825690128, 480807130959249565541
Offset: 0

Views

Author

David Callan, Oct 19 2005

Keywords

Comments

a(n) is the number of permutations on [n] that avoid the consecutive pattern 3412 (also number that avoid 2143).

Examples

			The 5! - a(5) = 10 permutations on [5] not counted by a(5) are 14523, 24513, 34125, 34512, 35124, 43512, 45123, 45132, 45231, 53412.
		

Crossrefs

Programs

  • Maple
    b:= proc(u, o, t) option remember; `if`(u+o=0, 1,
          add(b(u-j, o+j-1, `if`(t>0 and j>t, t-j, 0)), j=1..u)+
          add(b(u+j-1, o-j, j), j=`if`(t<0,1-t,1)..o))
        end:
    a:= n-> b(n, 0$2):
    seq(a(n), n=0..25);  # Alois P. Heinz, Nov 07 2013
  • Mathematica
    b[u_, o_, t_] := b[u, o, t] = If[u+o == 0, 1, Sum[b[u-j, o+j-1, If[t>0 && j>t, t-j, 0]], {j, 1, u}] + Sum[b[u+j-1, o-j, j], {j, Range[If[t<0, 1-t, 1], o]}]]; a[n_] := b[n, 0, 0]; Table[a[n], {n, 0, 25}] (* Jean-François Alcover, Mar 13 2015, after Alois P. Heinz *)

Formula

The Dotsenko et al. reference gives a g.f. There is an associated triangle of numbers c_{n,l} that should be added to the OEIS if it is not already present.
a(n) ~ c * d^n * n!, where d = 0.9561742431150784273897350385923872770208469..., c = 1.1465405299007850875068632404058971045769... . - Vaclav Kotesovec, Aug 23 2014

A201692 Number of permutations that avoid the consecutive pattern 1423.

Original entry on oeis.org

1, 1, 2, 6, 23, 110, 631, 4218, 32221, 276896, 2643883, 27768955, 318174363, 3949415431, 52794067318, 756137263377, 11551672922816, 187507250145806, 3222662529113641, 58464560588277289, 1116469710152742025, 22386721651323946628, 470259350616967829363
Offset: 0

Views

Author

N. J. A. Sloane, Dec 03 2011

Keywords

Crossrefs

Programs

  • Maple
    c := proc(n,l)
        if n = 1 then
            if l = 0 then
                1;
            else
                0;
            end if;
        elif n= 2 or n = 3 then
            0;
        else
            a := 0 ;
            for k from 1 to (n-2)/2 do
                a := a+procname(n-2*k-1,l-k)*binomial(n-k-2,k) ;
            end do:
            a ;
        end if;
    end proc:
    A201693 := proc(nmax)
        g := 1-t ;
        for n from 2 to nmax do
            for l from 0 to n/2 do
                g := g-c(n,l)*t^n*(-1)^l/n! ;
            end do:
        end do:
        taylor(1/g,t=0,nmax) ;
    end proc:
    nmax := 25 ;
    egf := A201693(nmax) ;
    for n from 0 to nmax-1 do
        printf("%d,",coeftayl(egf,t=0,n)*n!) ;
    end do: # R. J. Mathar, Dec 04 2011
    # second Maple program:
    b:= proc(u, o, t) option remember; `if`(u+o=0, 1,
          add(b(u-j, o+j-1, `if`(0 b(n, 0$2):
    seq(a(n), n=0..25);  # Alois P. Heinz, Nov 07 2013
  • Mathematica
    b[u_, o_, t_] := b[u, o, t] = If[u+o == 0, 1, Sum[b[u-j, o+j-1, If[0Jean-François Alcover, Mar 18 2014, after Alois P. Heinz *)

Formula

The reference gives an e.g.f. There is an associated triangle of numbers c_{n,l} that should be added to the OEIS if it is not already present.
a(n) ~ c * d^n * n!, where d = 0.95482605094987833345080179991528996596888600981..., c = 1.1567436851576902067739566662625378535625602... . - Vaclav Kotesovec, Sep 11 2014

Extensions

Definition corrected by N. J. A. Sloane, Mar 15 2015

A201693 Number of permutations that avoid the consecutive pattern 2413.

Original entry on oeis.org

1, 1, 2, 6, 23, 110, 632, 4237, 32465, 279828, 2679950, 28232972, 324470844, 4039771856, 54165468774, 778128659247, 11923645252411, 194131328012012, 3346615262190736, 60897160676005110, 1166446154857250412, 23459656378909613446, 494290181112325561351
Offset: 0

Views

Author

N. J. A. Sloane, Dec 03 2011

Keywords

Crossrefs

Formula

The reference gives a g.f. There is an associated triangle of numbers c_{n,l} that should be added to the OEIS if it is not already present.

Extensions

More terms from Ray Chandler, Dec 06 2011

A231166 Number of permutations of [n] avoiding simultaneously consecutive patterns 1243, 1342, and 1324.

Original entry on oeis.org

1, 1, 2, 6, 21, 91, 467, 2755, 18523, 139740, 1169616, 10763807, 108028386, 1174391384, 13748315494, 172439034531, 2306986699190, 32792999417180, 493559520202535, 7841127918788283, 131127477517244419, 2302491655047553206, 42355105188617740229
Offset: 0

Views

Author

Alois P. Heinz, Nov 04 2013

Keywords

Examples

			a(4) = 24 - 3 = 21 because 1243, 1342, 1324 are avoided.
		

Crossrefs

Programs

  • Maple
    b:= proc(u, o, s, t) option remember; `if`(u+o=0, 1,
           add(b(u-j, o+j-1, `if`(t>0, t, 0), `if`(t>0, -j, 0)),
               j=`if`(s>0 and t>0,s+t-1,1)..u)+
           add(b(u+j-1, o-j, `if`(t>0, t, 0), +j),
               j=1..`if`(s>0 and t<0 and -t b(n, 0$3):
    seq(a(n), n=0..25);
  • Mathematica
    b[u_, o_, s_, t_] := b[u, o, s, t] = If[u + o == 0, 1, Sum[b[u - j, o + j - 1, If[t > 0, t, 0], If[t > 0, -j, 0]], {j, If[s > 0 && t > 0, s + t - 1, 1], u}] + Sum[b[u + j - 1, o - j, If[t > 0, t, 0], +j], {j, 1, If[s > 0 && t < 0 && -t < s, -t - 1, o]}]];
    a[n_] := b[n, 0, 0, 0];
    a /@ Range[0, 25] (* Jean-François Alcover, Feb 27 2020, after Alois P. Heinz *)
Showing 1-8 of 8 results.