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 1-10 of 11 results. Next

A280780 Numerators of coefficients in asymptotic expansion of S_n (number of simple permutations, A111111).

Original entry on oeis.org

1, -4, 2, -40, -182, -7624, -202652, -14115088, -30800534, -16435427656, -1051314228316, -22675483971248, -6980651581556876, -283099764343781072, -163910651754113166328, -43009695328217994139936, -793529010007812171331166, -20144221762701827321778088, -274475989492312981198559876
Offset: 0

Views

Author

N. J. A. Sloane, Jan 19 2017

Keywords

Examples

			Coefficients are 1, -4, 2, -40/3, -182/3, -7624/15, -202652/45, -14115088/315, -30800534/63, -16435427656/2835, ...
		

Crossrefs

Programs

  • PARI
    seq(N) = {
      my(f = serreverse(x*Ser(vector(N, n, n!))));
      Vec(x* f'/f * exp(2 + (f-x)/(x*f)));
    };
    apply(numerator, seq(20))  \\ Gheorghe Coserea, Jan 22 2017

Formula

A111111(n) ~ n!*exp(-2)*(1 - 4/n + 2/(n*(n-1)) - (40/3)/(n*(n-1)*(n-2)) - ...). - Gheorghe Coserea, Jan 23 2017

Extensions

More terms from Gheorghe Coserea, Jan 22 2017

A280781 Denominators of coefficients in asymptotic expansion of S_n (number of simple permutations, A111111).

Original entry on oeis.org

1, 1, 1, 3, 3, 15, 45, 315, 63, 2835, 14175, 22275, 467775, 1216215, 42567525, 638512875, 638512875, 834978375, 558242685, 1856156927625, 713906510625, 17717861581875, 2143861251406875, 9861761756471625, 147926426347074375, 75472666503609375, 48076088562799171875
Offset: 0

Views

Author

N. J. A. Sloane, Jan 19 2017

Keywords

Comments

Has the same start as A046983 but is a different sequence.

Examples

			Coefficients are 1, -4, 2, -40/3, -182/3, -7624/15, -202652/45, -14115088/315, -30800534/63, -16435427656/2835, ...
		

Crossrefs

Programs

  • PARI
    seq(N) = {
      my(f = serreverse(x*Ser(vector(N, n, n!))));
      Vec(x* f'/f * exp(2 + (f-x)/(x*f)));
    };
    apply(denominator, seq(28))  \\ Gheorghe Coserea, Jan 22 2017

Extensions

More terms from Gheorghe Coserea, Jan 22 2017

A280777 Denominators of coefficients in asymptotic expansion of C_n (number of connected chord diagrams, A000699).

Original entry on oeis.org

1, 2, 8, 16, 128, 1280, 3072, 215040, 3440640, 2293760, 137625600, 201850880, 72666316800, 1889324236800, 52901078630400, 176336928768000, 135426761293824, 191854578499584000, 1593868805996544000, 787371190162292736000, 31494847606491709440000, 29395191099392262144000
Offset: 0

Views

Author

N. J. A. Sloane, Jan 19 2017

Keywords

Examples

			Coefficients are 1, -5/2, -43/8, -579/16, -44477/128, -5326191/1280, -180306541/3072, ...
		

Crossrefs

Programs

  • PARI
    A000699_seq(N) = {
      my(a = vector(N)); a[1] = 1;
      for (n=2, N, a[n] = sum(k=1, n-1, (2*k-1)*a[k]*a[n-k])); a;
    };
    seq(N) = my(C = 'x*Ser(A000699_seq(N))); Vec(x*exp(1-(2*C+C^2)/(2*x))/C);
    apply(denominator, seq(22)) \\ Gheorghe Coserea, Jan 22 2017

Extensions

More terms from Gheorghe Coserea, Jan 22 2017

A280778 Numerators of coefficients in asymptotic expansion of M_n (number of monolithic chord diagrams, A280775).

Original entry on oeis.org

1, -4, -6, -154, -1610, -34588, -4666292, -553625626, -1158735422, -388434091184, -31268175015478, -2796356409576766, -4624948938397276052, -1691272281281652408568, -2154089954877183990112, -170222948041126582837968646, -5761785676811885455064909606, -55629298859254851627617870836
Offset: 0

Views

Author

N. J. A. Sloane, Jan 19 2017

Keywords

Examples

			Coefficients are 1, -4, -6, -154/3, -1610/3, -34588/5, -4666292/45, -553625626/315, -1158735422/35, ...
		

Crossrefs

Programs

  • PARI
    A000699_seq(N) = {
      my(a = vector(N)); a[1] = 1;
      for (n=2, N, a[n] = sum(k=1, n-1, (2*k-1)*a[k]*a[n-k])); a;
    };
    seq(N) = {
      my(M = subst(x*Ser(A000699_seq(N)), x, x/(1-x)^2));
      Vec(x/(1-x)*exp(1-x/2-(1-x)^2/(2*x)*(2*M + M^2))/M);
    };
    apply(numerator, seq(18))  \\ Gheorghe Coserea, Jan 22 2017

Extensions

More terms from Gheorghe Coserea, Jan 22 2017

A280779 Denominators of coefficients in asymptotic expansion of M_n (number of monolithic chord diagrams, A280775).

Original entry on oeis.org

1, 1, 1, 3, 3, 5, 45, 315, 35, 567, 2025, 7425, 467775, 6081075, 257985, 638512875, 638512875, 172297125, 13956067125, 74246277105, 3093594879375, 14992036723125, 2143861251406875, 16436269594119375, 4226469324202125, 48028060502296875, 593531957565421875, 56437147443285984375
Offset: 0

Views

Author

N. J. A. Sloane, Jan 19 2017

Keywords

Comments

This has the same start as two other sequences, A241591 and A248592, but appears to be different from both.

Examples

			Coefficients are 1, -4,-6, -154/3, -1610/3, -34588/5, -4666292/45, -553625626/315, -1158735422/35, ...
		

Crossrefs

Programs

  • PARI
    A000699_seq(N) = {
      my(a = vector(N)); a[1] = 1;
      for (n=2, N, a[n] = sum(k=1, n-1, (2*k-1)*a[k]*a[n-k])); a;
    };
    seq(N) = {
      my(M = subst(x*Ser(A000699_seq(N)), x, x/(1-x)^2));
      Vec(x/(1-x)*exp(1-x/2-(1-x)^2/(2*x)*(2*M + M^2))/M);
    };
    apply(numerator, seq(18))  \\ Gheorghe Coserea, Jan 22 2017

A280776 Numerators of coefficients in asymptotic expansion of C_n (number of connected chord diagrams, A000699).

Original entry on oeis.org

1, -5, -43, -579, -44477, -5326191, -180306541, -203331297947, -58726239094693, -781618285277957, -1025587838964854273, -35763822710356866613, -330773478104531041960421, -237504847171108896327033959, -196526060612842999084524774697, -20633624138373135772483762873819
Offset: 0

Views

Author

N. J. A. Sloane, Jan 19 2017

Keywords

Examples

			Coefficients are 1, -5/2, -43/8, -579/16, -44477/128, -5326191/1280, -180306541/3072, ...
		

Crossrefs

Programs

  • PARI
    A000699_seq(N) = {
      my(a = vector(N)); a[1] = 1;
      for (n=2, N, a[n] = sum(k=1, n-1, (2*k-1)*a[k]*a[n-k])); a;
    };
    seq(N) = my(C = 'x*Ser(A000699_seq(N))); Vec(x*exp(1-(2*C+C^2)/(2*x))/C);
    apply(numerator, seq(16))  \\ Gheorghe Coserea, Jan 22 2017

Extensions

More terms from Gheorghe Coserea, Jan 22 2017

A244522 Number of simple involutions of length n.

Original entry on oeis.org

1, 1, 2, 0, 0, 2, 4, 10, 36, 126, 454, 1744, 6892, 28486, 120962, 531660, 2398248, 11127674, 52888998, 257570104, 1282439216
Offset: 0

Views

Author

Joerg Arndt and Jay Pantone, Jul 21 2014

Keywords

Examples

			The a(7) = 10 simple involutions are:
01:  [ 5 1 4 6 2 0 3 ]    (0, 5) (1) (2, 4) (3, 6)
02:  [ 4 1 6 3 0 5 2 ]    (0, 4) (1) (2, 6) (3) (5)
03:  [ 4 6 2 5 0 3 1 ]    (0, 4) (1, 6) (2) (3, 5)
04:  [ 5 3 6 1 4 0 2 ]    (0, 5) (1, 3) (2, 6) (4)
05:  [ 3 1 5 0 6 2 4 ]    (0, 3) (1) (2, 5) (4, 6)
06:  [ 3 5 2 0 6 1 4 ]    (0, 3) (1, 5) (2) (4, 6)
07:  [ 3 6 4 0 2 5 1 ]    (0, 3) (1, 6) (2, 4) (5)
08:  [ 2 5 0 3 6 1 4 ]    (0, 2) (1, 5) (3) (4, 6)
09:  [ 2 5 0 6 4 1 3 ]    (0, 2) (1, 5) (3, 6) (4)
10:  [ 2 4 0 6 1 5 3 ]    (0, 2) (1, 4) (3, 6) (5)
		

Crossrefs

Cf. A000085 (involutions), A111111 (simple permutations).

A359856 Number of permutations of [1..n] which are indecomposable by direct and skew sums.

Original entry on oeis.org

1, 1, 0, 0, 2, 22, 202, 1854, 17866, 183806, 2029850, 24081006, 306486314, 4175102110, 60708557626, 939518187726, 15430666746826, 268214861561726, 4921023843969242, 95066628485598126, 1929291834938927210, 41042364285004263262, 913409469123533445754, 21227246586149632119438
Offset: 0

Views

Author

Ludovic Schwob, Jan 16 2023

Keywords

Examples

			The only permutations of [1..4] which are indecomposable by direct and skew sums are 2413 and 3142.
		

Crossrefs

Programs

  • Mathematica
    nmax = 20; CoefficientList[Series[2*(2 - 1/Sum[k!*x^k, {k, 0, nmax}]) - Sum[k!*x^k, {k, 0, nmax}], {x, 0, nmax}], x] (* Vaclav Kotesovec, Jan 19 2023 *)
  • PARI
    seq(n)={my(p=sum(k=0, n, k!*x^k, O(x*x^n))); Vec(2*(2 - 1/p) - p)} \\ Andrew Howroyd, Jan 16 2023

Formula

G.f.: 2*(2 - 1/F(x)) - F(x) where F(x) = Sum_{k>=0} k!*x^k.
G.f.: S(F(x)) - 2*F(x)^2 - F(x) + x + 1 where S(x) is the g.f. of A111111 and F(x) = Sum_{k>=1} k!*x^k.
a(n) ~ n! * (1 - 4/n - 2/n^2 - 10/n^3 - 64/n^4 - 506/n^5 - 4762/n^6 - 51824/n^7 - 638678/n^8 - 8777898/n^9 - 132990772/n^10 - ...). - Vaclav Kotesovec, Jan 19 2023

A133262 Number of two-dimensional simple permutations.

Original entry on oeis.org

1, 4, 8, 172, 5204, 222716, 12509188, 889421564, 78097622276, 8312906703868, 1056520142488580, 158263730949406716, 27626236450406776836, 5563092167972597137404, 1280742543230231763615748, 334405228960123174787678204, 98317121153947856929753989124, 32339023133437156084762282819580, 11831483864832785151824395066146820, 4789379698138059405310741712024371196
Offset: 1

Views

Author

Hao Zhang and Daniel Gildea (zhanghao(AT)cs.rochester.edu), Oct 15 2007

Keywords

Comments

A two-dimensional permutation of n is a vector of three permutations, with the first element being the identity permutation. For example, ( (1 2 3) (1 3 2) (3 1 2) ) is a two-dimensional permutation of 3. The example is a simple two-dimensional permutation because none of the intervals of length 2 in the permutations is common among all three. On the other hand, ( (1 2 3) (1 3 2) (2 3 1) ) is not simple because the intervals covering 2 and 3 are common among all three permutations.

Crossrefs

Extensions

More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Feb 10 2008

A198434 Number of simple symmetric permutations of degree 2n (or 2n+1).

Original entry on oeis.org

2, 10, 90, 966, 12338, 181470, 3018082, 55995486, 1146939010, 25716746430, 626755197698, 16502357651966, 466944932413442, 14133259249586174, 455715081098876418, 15596665064842012158, 564724372634695925762, 21568978799171323200510, 866674159679235417061378, 36548294282449538711357438
Offset: 2

Views

Author

David Wehlau, Oct 24 2011

Keywords

Comments

A permutation is simple if the only intervals that are fixed are the singletons and [1..m].
A permutation p is symmetric if i+j=m+1 implies p(i)+p(j)=m+1.
For example the permutations
1234 and 12345
2413 25314
are both simple and symmetric.
Symmetric simple permutations of degree 2n+1 correspond to simple permutations in the Weyl group of type B_n.
Symmetric simple permutations of degree 2n correspond to simple permutations in the Weyl group of type C_n.
These occur in pairs so all entries in this sequence will be even.

Examples

			The simple symmetric permutations of lowest degree are 2413, 3142, 25314, 41325.
		

Crossrefs

Cf. A111111.
Showing 1-10 of 11 results. Next