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.

A141753 Main diagonal of A139755, the table of q-derangement numbers of type A.

Original entry on oeis.org

1, 1, 2, 7, 24, 86, 313, 1157, 4325, 16303, 61856, 235917, 903620, 3473381, 13391280, 51761781, 200523644, 778342906, 3026400508, 11785538461, 45959004812, 179444813270, 701422450293, 2744562302533, 10749124666643, 42135320616531
Offset: 1

Views

Author

Paul D. Hanna, Jul 05 2008

Keywords

Crossrefs

Programs

  • PARI
    {a(n)=polcoeff(prod(j=1,n+1,(1-q^j)/(1-q))* sum(k=0,n+1,(-1)^k*q^(k*(k-1)/2)/if(k==0,1,prod(j=1,k,(1-q^j)/(1-q)))),n,q)}

Formula

a(n) = [q^n] { ([n+1]q)! * Sum{m=0..n+1} (-1)^m * q^(m(m-1)/2) / ([m]q)! }; here, the q-factorial of n is denoted by ([n]_q)! = Product{j=1..n} (1-q^j)/(1-q).
a(n) ~ c * 4^n / sqrt(Pi*n), where c = A048651^2 = QPochhammer(1/2)^2 = 0.083398563863748521534541808155312... - Vaclav Kotesovec, Aug 30 2023

A141754 Secondary diagonal of A139755, the table of q-derangement numbers of type A.

Original entry on oeis.org

1, 2, 5, 16, 54, 190, 684, 2505, 9291, 34793, 131277, 498312, 1900862, 7280732, 27983141, 107868939, 416869874, 1614609446, 6265869591, 24358231651, 94837442844, 369755864507, 1443420649734, 5641088964709, 22068939198169
Offset: 1

Views

Author

Paul D. Hanna, Jul 05 2008

Keywords

Crossrefs

Programs

  • PARI
    {a(n)=polcoeff(prod(j=1,n+2,(1-q^j)/(1-q))* sum(k=0,n+2,(-1)^k*q^(k*(k-1)/2)/if(k==0,1,prod(j=1,k,(1-q^j)/(1-q)))),n,q)}

Formula

a(n) = [q^n] { ([n+2]q)! * Sum{m=0..n+2} (-1)^m * q^(m(m-1)/2) / ([m]q)! }; here, the q-factorial of n is denoted by ([n]_q)! = Product{j=1..n} (1-q^j)/(1-q), with ([0]_q)! = 1.
a(n) ~ c * 4^n / sqrt(Pi*n), where c = 2*QPochhammer(1/2)^2 = 0.166797127727497043069083616310625... - Vaclav Kotesovec, Aug 30 2023, updated Mar 17 2024

A140075 Table of q-derangement numbers of type B, by rows.

Original entry on oeis.org

1, 1, 2, 1, 1, 1, 3, 4, 5, 5, 4, 4, 2, 1, 1, 4, 8, 13, 18, 22, 26, 28, 28, 25, 21, 17, 11, 7, 3, 1
Offset: 1

Views

Author

Jonathan Vos Post, Jun 14 2008

Keywords

Comments

This sequence is from Table 1.2 of Chen and Wang, p. 3.

Examples

			The table begins:
===================================================================================
k=...|.1.|.2.|.3.|..4.|..5.|..6.|..7.|..8.|..9.|.10.|.11.|.12.|.13.|.14.|.15.|.16.|
===================================================================================
n=1..|.1.|
n=2..|.1.|.2.|.1.|..1.|
n=3..|.1.|.3.|.4.|..5.|..5.|..4.|..4.|..2.|..1.|
n=4..|.1.|.4.|.8.|.13.|.18.|.22.|.26.|.28.|.28.|.25.|.21.|.17.|.11.|..7.|..3.|..1.|
===================================================================================
		

Crossrefs

Showing 1-3 of 3 results.