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: Vincent Vatter

Vincent Vatter's wiki page.

Vincent Vatter has authored 57 sequences. Here are the ten most recent ones:

A342474 Minimal length of a permutation containing every permutation of length n as a pattern.

Original entry on oeis.org

1, 3, 5, 9, 13, 17
Offset: 1

Author

Vincent Vatter, Mar 13 2021

Keywords

Comments

These permutations are sometimes called "superpatterns".
A upper bound is ceiling((n^2+1)/2), see Engen and Vatter. A simple lower bound is n^2/e^2, which has been improved to 1.000076 n^2/e^2 by Chroman, Kwan, and Singhal.

Examples

			For n=3, the permutation 25314 contains all 6 permutations of length 3, but no shorter permutation does, so a(3)=5.
		

Crossrefs

A256181 The number of permutations of length n sortable by 3 block interchanges.

Original entry on oeis.org

1, 2, 6, 24, 120, 720, 5040, 32256, 169632, 737364, 2731444, 8875868, 25894376, 69053375, 170694383, 395443223, 866147111, 1806459866, 3608498678, 6937282452, 12887902732, 23216767894, 40675018726, 69480583966, 115975600846, 189528370396, 303753983092
Offset: 1

Author

Vincent Vatter, Apr 03 2015

Keywords

Examples

			The shortest permutations that cannot be sorted by 3 block interchanges are of length 8.
		

Crossrefs

Programs

  • PARI
    Vec(x*(1-11*x+58*x^2-184*x^3+419*x^4-541*x^5+1608*x^6-270*x^7+567*x^8-217*x^9+66*x^10-12*x^11+x^12)/(1-x)^13 + O(x^30)) \\ Colin Barker, Dec 15 2015

Formula

G.f.: -x * (x^12 -12*x^11 +66*x^10 -217*x^9 +567*x^8 -270*x^7 +1608*x^6 -541*x^5 +419*x^4 -184*x^3 +58*x^2 -11*x +1) / (x^13 -13*x^12 +78*x^11 -286*x^10 +715*x^9 -1287*x^8 +1716*x^7 -1716*x^6 +1287*x^5 -715*x^4 +286*x^3 -78*x^2 +13*x -1).

A228396 The number of permutations of length n sortable by 2 reversals.

Original entry on oeis.org

1, 1, 2, 6, 22, 63, 145, 288, 516, 857, 1343, 2010, 2898, 4051, 5517, 7348, 9600, 12333, 15611, 19502, 24078, 29415, 35593, 42696, 50812, 60033, 70455, 82178, 95306, 109947, 126213, 144220, 164088, 185941, 209907, 236118, 264710, 295823, 329601, 366192, 405748
Offset: 0

Author

Vincent Vatter, Aug 21 2013

Keywords

Examples

			There are 2 permutations of length 4 which cannot be sorted by 2 reversals.
		

Crossrefs

Programs

  • Mathematica
    CoefficientList[Series[(1/x) (-1 - (x^7 - x^6 - 3 x^5 + 7 x^4 - 4 x^3 + 7 x^2 - 4 x + 1)/(x - 1)^5), {x, 0, 40}], x] (* Bruno Berselli, Aug 22 2013 *)
    LinearRecurrence[{5,-10,10,-5,1},{1,2,6,22,63,145,288},40] (* Harvey P. Dale, Mar 08 2019 *)

Formula

G.f.: -(x^7 - x^6 - 3*x^5 + 7*x^4 - 4*x^3 + 7*x^2 - 4*x + 1)/(x - 1)^5.
a(n) = 8 + n*(n^3 -2*n^2 +2*n -19)/6 for n>2, a(1)=1, a(2)=2. [Bruno Berselli, Aug 22 2013]

Extensions

a(0)=1 prepended by Alois P. Heinz, Mar 31 2025

A228398 The number of permutations of length n sortable by 3 prefix reversals (in the pancake sorting sense).

Original entry on oeis.org

1, 2, 6, 21, 52, 105, 186, 301, 456, 657, 910, 1221, 1596, 2041, 2562, 3165, 3856, 4641, 5526, 6517, 7620, 8841, 10186, 11661, 13272, 15025, 16926, 18981, 21196, 23577, 26130, 28861, 31776, 34881, 38182, 41685, 45396, 49321, 53466, 57837, 62440, 67281, 72366
Offset: 1

Author

Vincent Vatter, Aug 21 2013

Keywords

Comments

Essentially the same as A069778.

Examples

			There are only 3 permutations of length 4 which cannot be sorted by 3 pancake reversals.
		

Crossrefs

Programs

  • Mathematica
    CoefficientList[Series[(1/x) (-1 + (x^6 - 3 x^5 + 6 x^4 + 4 x^2 - 3 x + 1)/(x - 1)^4), {x, 0, 50}], x] (* Bruno Berselli, Aug 22 2013 *)

Formula

G.f.: -1 + (x^6 - 3*x^5 + 6*x^4 + 4*x^2 - 3*x + 1)/(x - 1)^4.
a(n) = (n-1)*(n^2-3*n+3) for n>2, a(1)=1, a(2)=2. [Bruno Berselli, Aug 22 2013]

A228394 The number of permutations of length n sortable by 2 prefix block transpositions.

Original entry on oeis.org

1, 2, 6, 21, 61, 146, 302, 561, 961, 1546, 2366, 3477, 4941, 6826, 9206, 12161, 15777, 20146, 25366, 31541, 38781, 47202, 56926, 68081, 80801, 95226, 111502, 129781, 150221, 172986, 198246, 226177, 256961, 290786, 327846, 368341, 412477, 460466, 512526, 568881
Offset: 1

Author

Vincent Vatter, Aug 21 2013

Keywords

Examples

			There are 3 permutations of length 4 that cannot be sorted by 2 prefix block transpositions.
		

Crossrefs

Programs

  • Mathematica
    CoefficientList[Series[(1/x) (-1 - (x^2 + 1) (6 x^2 - 4 x + 1)/(x - 1)^5), {x, 0, 50}], x] (* Bruno Berselli, Aug 22 2013 *)
    LinearRecurrence[{5,-10,10,-5,1},{1,2,6,21,61},40] (* Harvey P. Dale, May 28 2018 *)

Formula

G.f.: -1 -(x^2 + 1)*(6*x^2 - 4*x + 1)/(x - 1)^5.
a(n) = 1 + (n-1)*n*(3*n^2-11*n+16)/12. [Bruno Berselli, Aug 22 2013]

A228397 The number of permutations of length n sortable by 3 reversals.

Original entry on oeis.org

1, 2, 6, 24, 118, 534, 1851, 5158, 12264, 25943, 50214, 90656, 154758, 252304, 395793, 600894, 886936, 1277433, 1800644, 2490168, 3385574, 4533066, 5986183, 7806534, 10064568, 12840379, 16224546, 20319008, 25237974, 31108868, 38073309, 46288126, 55926408
Offset: 1

Author

Vincent Vatter, Aug 21 2013

Keywords

Examples

			There are 2 permutations of length 5 which cannot be sorted by 3 reversals.
		

Crossrefs

Programs

  • Mathematica
    CoefficientList[Series[(1/x) (-1 - (2 x^10 + 5 x^9 + 12 x^8 - 75 x^7 + 58 x^6 + 20 x^5 + 24 x^4 - 22 x^3 + 16 x^2 - 6 x + 1)/(x - 1)^7), {x, 0, 50}], x] (* Bruno Berselli, Aug 22 2013 *)

Formula

G.f.: -1 -(2*x^10 + 5*x^9 + 12*x^8 - 75*x^7 + 58*x^6 + 20*x^5 + 24*x^4 - 22*x^3 + 16*x^2 - 6*x + 1)/(x - 1)^7.
a(n) = n! for 0 < n < 4; for n > 3, a(n) = 318 + n*(7*n^5 -21*n^4 -125*n^3 -819*n^2 +12862*n -42720)/144. [Bruno Berselli, Aug 22 2013]

A228399 The number of permutations of length n sortable by 2 cut-and-paste moves.

Original entry on oeis.org

1, 2, 6, 24, 120, 577, 2208, 6768, 17469, 39603, 81272, 154225, 274802, 464985, 753556, 1177362, 1782687, 2626731, 3779196, 5323979, 7360972, 10007969, 13402680, 17704852, 23098497, 29794227, 38031696, 48082149, 60251078, 74880985, 92354252, 113096118
Offset: 1

Author

Vincent Vatter, Aug 21 2013

Keywords

Examples

			The shortest permutations which cannot be sorted by 2 cut-and-paste moves are of length 6.
		

Crossrefs

Programs

  • Mathematica
    CoefficientList[Series[(1/x) (-1 + (x^11 - 5 x^10 - 2 x^9 + 44 x^8 - 23 x^7 - 87 x^6 - 22 x^5 - 24 x^4 + 22 x^3 - 16 x^2 + 6 x - 1)/(x - 1)^7), {x,
       0, 40}], x] (* Bruno Berselli, Aug 22 2013 *)

Formula

G.f.: -1 + (x^11 - 5*x^10 - 2*x^9 + 44*x^8 - 23*x^7 - 87*x^6 - 22*x^5 - 24*x^4 + 22*x^3 - 16*x^2 + 6*x - 1)/(x - 1)^7.
a(n) = n! for 0 < n < 5; for n > 4, a(n) = -18 + n*(107*n^5 -1077*n^4 +2225*n^3 +12345*n^2 -61732*n +80532)/720. [Bruno Berselli, Aug 22 2013]

A228393 The number of permutations of length n that can be sorted by 3 block transpositions.

Original entry on oeis.org

1, 2, 6, 24, 120, 675, 3527, 15484, 56917, 179719, 500864, 1260117, 2913132, 6274230, 12726573, 24521243, 45190897, 80108200, 137224138, 228026582, 368765112, 581994117, 898492563, 1359625566, 2020220021, 2952034021, 4247907652, 6026690971, 8439053564
Offset: 1

Author

Vincent Vatter, Aug 21 2013

Keywords

Examples

			The shortest permutations which cannot be sorted by 3 block transpositions are of length 6.
		

Crossrefs

Programs

  • Mathematica
    CoefficientList[Series[-(x^9 - 9 x^8 - 17 x^7 - 263 x^6 - 3 x^5 - 120 x^4 + 66 x^3 - 31 x^2 + 8 x - 1)/(x - 1)^10, {x, 0, 40}], x] (* Bruno Berselli, Aug 22 2013 *)

Formula

G.f.: -x*(x^9 - 9*x^8 - 17*x^7 - 263*x^6 - 3*x^5 - 120*x^4 + 66*x^3 - 31*x^2 + 8*x - 1)/(x - 1)^10.

A228392 The number of permutations of length n sortable by 2 block transpositions.

Original entry on oeis.org

1, 2, 6, 23, 89, 295, 827, 2017, 4405, 8812, 16424, 28887, 48413, 77897, 121045, 182513, 268057, 384694, 540874, 746663, 1013937, 1356587, 1790735, 2334961, 3010541, 3841696, 4855852, 6083911, 7560533, 9324429, 11418665, 13890977, 16794097, 20186090, 24130702, 28697719, 33963337, 40010543
Offset: 1

Author

Vincent Vatter, Aug 21 2013

Keywords

Examples

			The shortest permutation which cannot be sorted by 2 block transpositions is of length 4.
		

Crossrefs

Programs

  • PARI
    Vec(-1-(x^6-2*x^5+23*x^4-22*x^3+16*x^2-6*x+1)/(x-1)^7 + O(x^50)) \\ Michel Marcus, Apr 03 2015

Formula

G.f.: -1 -(x^6 - 2*x^5 + 23*x^4 - 22*x^3 + 16*x^2 - 6*x + 1)/(x - 1)^7.

A228401 The number of permutations of length n sortable by 2 block interchanges.

Original entry on oeis.org

1, 2, 6, 24, 120, 540, 1996, 6196, 16732, 40459, 89519, 184185, 356721, 656475, 1156443, 1961563, 3219019, 5130856, 7969228, 12094622, 17977422, 26223198, 37602126, 53082966, 73872046, 101457721, 137660797, 184691431, 245213039, 322413765, 420086085, 542715141
Offset: 1

Author

Vincent Vatter, Aug 21 2013

Keywords

Examples

			The shortest permutations that cannot be sorted by 2 block interchanges are of length 7.
		

Crossrefs

Programs

  • Mathematica
    CoefficientList[Series[-(x^8 - 8 x^7 + 28 x^6 - 54 x^5 + 78 x^4 - 42 x^3 + 24 x^2 - 7 x + 1)/(x - 1)^9, {x, 0, 40}], x] (* Bruno Berselli, Aug 22 2013 *)
    LinearRecurrence[{9,-36,84,-126,126,-84,36,-9,1},{1,2,6,24,120,540,1996,6196,16732},40] (* Harvey P. Dale, Dec 31 2019 *)

Formula

G.f.: -x*(x^8 -8*x^7 +28*x^6 -54*x^5 +78*x^4 -42*x^3 +24*x^2 -7*x +1)/(x-1)^9.
a(n) = 1 + n*(n-1)*(n+1)*(n+2)*(3*n^4-10*n^3-11*n^2+50*n+216)/5760. [Bruno Berselli, Aug 22 2013]