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.

A276837 Number A(n,k) of permutations of [n] such that for each cycle c the smallest integer interval containing all elements of c has at most k elements; square array A(n,k), n>=0, k>=0, read by antidiagonals.

Original entry on oeis.org

1, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1, 1, 2, 1, 0, 1, 1, 2, 3, 1, 0, 1, 1, 2, 6, 5, 1, 0, 1, 1, 2, 6, 12, 8, 1, 0, 1, 1, 2, 6, 24, 25, 13, 1, 0, 1, 1, 2, 6, 24, 60, 57, 21, 1, 0, 1, 1, 2, 6, 24, 120, 150, 124, 34, 1, 0, 1, 1, 2, 6, 24, 120, 360, 399, 268, 55, 1, 0
Offset: 0

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Author

Alois P. Heinz, Sep 20 2016

Keywords

Comments

The sequence of column k satisfies a linear recurrence with constant coefficients of order 2^(k-1) for k>0.

Examples

			Square array A(n,k) begins:
  1, 1,  1,   1,    1,    1,    1,     1,     1, ...
  0, 1,  1,   1,    1,    1,    1,     1,     1, ...
  0, 1,  2,   2,    2,    2,    2,     2,     2, ...
  0, 1,  3,   6,    6,    6,    6,     6,     6, ...
  0, 1,  5,  12,   24,   24,   24,    24,    24, ...
  0, 1,  8,  25,   60,  120,  120,   120,   120, ...
  0, 1, 13,  57,  150,  360,  720,   720,   720, ...
  0, 1, 21, 124,  399, 1050, 2520,  5040,  5040, ...
  0, 1, 34, 268, 1145, 3192, 8400, 20160, 40320, ...
		

Crossrefs

Main diagonal gives A000142.

Formula

A(n,k+1) - A(n,k) = A263757(n,k) for n>0.

A263597 T(n,k)=Number of length n arrays of permutations of 0..n-1 with each element moved by -k to k places and the median of every three consecutive elements nondecreasing.

Original entry on oeis.org

1, 1, 2, 1, 2, 3, 1, 2, 6, 5, 1, 2, 6, 12, 8, 1, 2, 6, 16, 25, 13, 1, 2, 6, 16, 41, 57, 21, 1, 2, 6, 16, 52, 108, 124, 34, 1, 2, 6, 16, 52, 164, 280, 268, 55, 1, 2, 6, 16, 52, 208, 476, 729, 588, 89, 1, 2, 6, 16, 52, 208, 676, 1428, 1908, 1285, 144, 1, 2, 6, 16, 52, 208, 800, 2208, 4308
Offset: 1

Views

Author

R. H. Hardin, Oct 22 2015

Keywords

Comments

Table starts
..1....1....1.....1.....1.....1.....1.....1.....1.....1.....1.....1.....1.....1
..2....2....2.....2.....2.....2.....2.....2.....2.....2.....2.....2.....2.....2
..3....6....6.....6.....6.....6.....6.....6.....6.....6.....6.....6.....6.....6
..5...12...16....16....16....16....16....16....16....16....16....16....16....16
..8...25...41....52....52....52....52....52....52....52....52....52....52....52
.13...57..108...164...208...208...208...208...208...208...208...208...208...208
.21..124..280...476...676...800...800...800...800...800...800...800...800...800
.34..268..729..1428..2208..2900..3360..3360..3360..3360..3360..3360..3360..3360
.55..588.1908..4308..7696.10960.14024.16224.16224.16224.16224.16224.16224.16224
.89.1285.4969.12816.25508.40792.55492.69212.78088.78088.78088.78088.78088.78088

Examples

			Some solutions for n=6 k=4
..1....1....1....0....2....0....0....0....1....4....3....2....1....4....0....2
..2....2....0....1....1....5....3....1....5....1....1....0....4....0....1....0
..3....3....2....3....5....2....2....2....0....0....0....1....0....1....3....1
..0....0....4....4....3....3....1....5....2....2....2....5....3....3....5....3
..4....5....3....2....0....4....4....3....4....3....4....3....5....2....2....4
..5....4....5....5....4....1....5....4....3....5....5....4....2....5....4....5
		

Crossrefs

Column 1 is A000045(n+1).
Column 2 is A214663.

Formula

Empirical for column k:
k=1: a(n) = a(n-1) +a(n-2)
k=2: a(n) = a(n-1) +a(n-2) +3*a(n-3) +a(n-4)
k=3: a(n) = a(n-1) +a(n-2) +7*a(n-3) +2*a(n-4) +4*a(n-5) -a(n-7) -a(n-8)
k=4: [order 15]
k=5: [order 31]
k=6: [order 67]

A232164 Number of Weyl group elements, not containing an s_r factor, which contribute nonzero terms to Kostant's weight multiplicity formula when computing the multiplicity of the zero-weight in the adjoint representation for the Lie algebra of type C and rank n.

Original entry on oeis.org

0, 1, 1, 2, 6, 12, 25, 57, 124, 268, 588, 1285, 2801, 6118, 13362, 29168, 63685, 139057, 303608, 662888, 1447352, 3160121, 6899745, 15064810, 32892270, 71816436, 156802881, 342360937, 747505396, 1632091412, 3563482500, 7780451037, 16987713169, 37090703118
Offset: 0

Views

Author

Pamela E Harris, Nov 19 2013

Keywords

Comments

Apart from the offset the same as A214663. - R. J. Mathar, Nov 27 2013
Apart from the initial 0, number of permutations of length n>=0 avoiding the partially ordered pattern (POP) {1>4} of length 4. That is, number of length n permutations having no subsequences of length 4 in which the first element is larger than the last element. - Sergey Kitaev, Dec 08 2020

Examples

			For n=4, a(4)= A232164(3) + A232164(2) + 3*A232164(1) + A232164(0) = 2+1+3*1+0=6.
		

References

  • P. E. Harris, Combinatorial problems related to Kostant's weight multiplicity formula, PhD Dissertation, University of Wisconsin-Milwaukee, 2012.

Programs

  • Maple
    a:=proc(n::nonnegint)
    if n=0 then return 0:
    elif n=1 then return 1:
    elif n=2 then return 1:
    elif n=3 then return 2:
    else return
    a(n-1)+a(n-2)+3*a(n-3)+a(n-4):
    end if;
    end proc:
  • Mathematica
    CoefficientList[Series[x/(1 - x - x^2 -3 x^3- x^4),{x, 0, 30}], x] (* Vincenzo Librandi, Dec 31 2013 *)
  • PARI
    Vec(-x/(x^4+3*x^3+x^2+x-1) + O(x^100)) \\ Colin Barker, Dec 31 2013

Formula

a(n) = A232164(n-1) + A232164(n-2) + 3*A232164(n-3) + A232164(n-4).
From Colin Barker, Dec 31 2013: (Start)
a(n) = a(n-1) + a(n-2) + 3*a(n-3) + a(n-4).
G.f.: -x/(x^4 + 3*x^3 + x^2 + x - 1). (End)
Showing 1-3 of 3 results.