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 1-3 of 3 results.

A071075 Number of permutations that avoid the generalized pattern 132-4.

Original entry on oeis.org

1, 1, 2, 6, 23, 107, 585, 3671, 25986, 204738, 1776327, 16824237, 172701135, 1909624371, 22626612450, 285982186662, 3840440707485, 54603776221965, 819424594880559, 12942757989763101, 214626518776190178, 3728112755679416898, 67692934780306842501, 1282399636333412178531, 25303124674163685176793
Offset: 0

Views

Author

Sergey Kitaev, May 26 2002

Keywords

Crossrefs

Programs

  • Maple
    A(y) := 1/(1-int(exp(-t^2/2),t=0..y)); B(x) := exp(int(A(y),y=0..x)); series(B(x),x=0,30);
  • Mathematica
    CoefficientList[Series[E^(Integrate[1/(1-Integrate[E^(-t^2/2), {t,0,y}]), {y,0,x}]), {x, 0, 20}], x] * Range[0, 20]! (* Vaclav Kotesovec, Aug 23 2014 *)
  • PARI
    N=66; x='x+O('x^N);
    A=1/(1-intformal(exp(-x^2/2)));
    egf=exp(intformal(A));
    Vec(serlaplace(egf))
    \\ Joerg Arndt, Aug 28 2014

Formula

E.g.f.: exp(int(A(y), y=0..x)), where A(y) = 1/(1 - int(exp(-t^2/2), t=0..y)).
a(n) ~ c * d^n * n! / n^f, where d = 1/A240885 = 1/(sqrt(2)*InverseErf(sqrt(2/Pi))) = 0.7839769312035474991242486548698125357473282..., f = 1.2558142944089303287268746534354522944538722816671534535062816..., c = 0.2242410644782853722452053227678681810005068... . - Vaclav Kotesovec, Aug 23 2014
Let b(n) = A111004(n) = number of permutations of [n] that avoid the consecutive pattern 132. Then a(n) = Sum_{i = 0..n-1} binomial(n-1,i)*b(i)*a(n-1-i) with a(0) = b(0) = 1. [See the recurrence for A_n and B_n in the proof of Theorem 13 in Kitaev's papers.] - Petros Hadjicostas, Nov 01 2019

Extensions

Link and a(11)-a(20) from Andrew Baxter, May 17 2011
Typo in first formula corrected by Vaclav Kotesovec, Aug 23 2014

A071077 Number of permutations that avoid the generalized pattern 1234-5.

Original entry on oeis.org

1, 1, 2, 6, 24, 119, 705, 4857, 38142, 336291, 3289057, 35337067, 413698248, 5241768017, 71465060725, 1043175024243, 16231998346794, 268207096127991, 4690005160446721, 86528908665043683, 1679764981327051508, 34226671269330933413, 730361830628447403029
Offset: 0

Views

Author

Sergey Kitaev, May 26 2002

Keywords

Crossrefs

Programs

  • Maple
    b:= proc(u, o, t) option remember; `if`(u+o=0, 1, add(
          `if`(t=2 and o>j, 0, b(u+j-1, o-j, t+1)), j=1..o)+
           add(b(u-j, o+j-1, 0), j=1..u))
        end:
    a:= n-> b(n, 0$2):
    seq(a(n), n=0..25);  # Alois P. Heinz, Nov 14 2015
  • Mathematica
    b[u_, o_, t_] := b[u, o, t] = If[u+o == 0, 1, Sum[If[t == 2 && o>j, 0, b[u+j-1, o-j, t+1]], {j, 1, o}] + Sum[b[u-j, o+j-1, 0], {j, 1, u}]];
    a[n_] := b[n, 0, 0];
    a /@ Range[0, 25] (* Jean-François Alcover, Apr 23 2020, after Alois P. Heinz *)

Formula

E.g.f.: exp(int(A(y), y=0..x)), where A(y) = 1/(Sum_{i>=0} y^{4*i}/(4*i)! - Sum_{i>=0} y^{4*i+1}/(4*i+1)!).
Let b(n) = A117158(n) = number of permutations of [n] that avoid the consecutive pattern 1234. Then a(n) = Sum_{i = 0..n-1} binomial(n-1,i)*b(i)*a(n-1-i) with a(0) = b(0) = 1. [See the recurrence for A_n and B_n in the proof of Theorem 13 in Kitaev's papers.] - Petros Hadjicostas, Oct 31 2019

Extensions

Corrected and extended by Vladeta Jovovic, May 28 2002

A071088 Number of permutations that avoid the generalized pattern 12345-6.

Original entry on oeis.org

1, 1, 2, 6, 24, 120, 719, 5022, 40064, 359400, 3580896, 39233867, 468818397, 6067548429, 84551873634, 1262188317534, 20095114167065, 339883289813330, 6086154606429378, 115025120586250896, 2288119443771888504, 47787869441095495395, 1045507132393256095282
Offset: 0

Views

Author

Sergey Kitaev, May 26 2002

Keywords

Crossrefs

Programs

  • Maple
    b:= proc(u, o, t) option remember; `if`(u+o=0, 1, add(
          `if`(t=3 and o>j, 0, b(u+j-1, o-j, t+1)), j=1..o)+
           add(b(u-j, o+j-1, 0), j=1..u))
        end:
    a:= n-> b(n, 0$2):
    seq(a(n), n=0..25);  # Alois P. Heinz, Nov 14 2015
  • Mathematica
    b[u_, o_, t_] := b[u, o, t] = If[u+o == 0, 1, Sum[If[t == 3 && o > j, 0, b[u+j-1, o-j, t+1]], {j, 1, o}] + Sum[b[u-j, o+j-1, 0], {j, 1, u}]];
    a[n_] := b[n, 0, 0];
    a /@ Range[0, 25] (* Jean-François Alcover, Nov 02 2020, after Alois P. Heinz *)

Formula

E.g.f.: exp(int(A(y), y=0..x)), where A(y) = 1/(Sum_{i>=0} y^{5*i}/(5*i)! - Sum_{i>=0} y^{5*i+1}/(5*i+1)!).
Let b(n) = A177523(n) = number of permutations of [n] that avoid the consecutive pattern 12345. Then a(n) = Sum_{i = 0..n-1} binomial(n-1,i)*b(i)*a(n-1-i) with a(0) = b(0) = 1. [See the recurrence for A_n and B_n in the proof of Theorem 13 in Kitaev's papers.] - Petros Hadjicostas, Nov 01 2019

Extensions

More terms from Vladeta Jovovic, May 28 2002
Showing 1-3 of 3 results.