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.

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A089225 Triangle T(n,k) read by rows, defined by T(n,k) = (n-k)*T(n-1,k)+Sum(k=1..n, T(n-1,k)); T(1,1) = 1, T(1,k)= 0 if k >1.

Original entry on oeis.org

1, 2, 1, 7, 4, 3, 35, 22, 17, 14, 228, 154, 122, 102, 88, 1834, 1310, 1060, 898, 782, 694, 17582, 13128, 10818, 9272, 8142, 7272, 6578, 195866, 151560, 126882, 109880, 97218, 87336, 79370, 72792, 2487832, 1981824, 1682196, 1470304, 1309776
Offset: 1

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Author

Philippe Deléham, Dec 10 2003

Keywords

Comments

Let M be the n X n matrix with M(i,i)=i, other entries 1. Then T(n,k) = permanent of n-1 X n-1 matrix obtained by omitting row k and column k from M.
T(n,1) = A003713(n). n-th row sum = T(n+1,n+1) = A007840(n). {1}, {2, 1}, {7, 4, 3}, {35, 22, 17, 14}, ...

Examples

			n=4: M = |1,1,1,1|1, 2,1, 1|1, 1, 3, 1|1, 1, 1, 4|
T(4, 1) = permanent of |2, 1, 1|1, 3, 1|1, 1, 4| = 26+5+4 = 35
T(4, 2) = permanent of |1, 1, 1|1, 3, 1|1, 1, 4| = 13+5+4 = 22
T(4, 3) = permanent of |1, 1, 1|1, 2, 1|1, 1, 4| = 9+5+3 = 17
T(4, 4) = permanent of |1, 1, 1|1, 2, 1|1, 1, 3| = 7+4+3 = 14
		

A091739 Third column (k=7) sequence of array A090216 ((5,5)-Stirling2) divided by 600.

Original entry on oeis.org

1, 4440, 12715200, 33158592000, 84365452800000, 213181366579200000, 537634980016128000000, 1355141067314135040000000, 3415172150786516582400000000, 8606389816065144913920000000000
Offset: 0

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Author

Wolfdieter Lang, Feb 13 2004

Keywords

Crossrefs

Cf. A091553 (third column of array (4, 4)-Stirling2 divided by 72).

Formula

a(n)= A090216(n+2, 7)/600, n>=0.
a(n)= ((5!)^n)*(1-2*6^(n+1)+binomial(7, 2)^(n+1))/(2*5). From eq.12 of the Blasiak et al. reference given in A007840 with r=5=s, k=7.
a(n)= (21*(7*6*5*4*3)^n - 12*(6*5*4*3*2)^n + (5*4*3*2*1)^n)/10.
G.f.: (1+1080*x)/product(1-fallfac(p, 5)*x, p=5..7), with fallfac(n, m) := A008279(n, m) (falling factorials).

A248028 a(n) = Sum_{k=0..n} |Stirling1(n, k)|*(n-k)! for n>=0.

Original entry on oeis.org

1, 1, 2, 8, 65, 957, 22512, 773838, 36561289, 2271696241, 179538792358, 17584290721868, 2090031277816649, 296326507395472205, 49400463740287289892, 9566059122999739401954, 2129221864475839211318769, 539805407803681202368358785, 154636541536285163968515043306, 49702496963149041682740769491568
Offset: 0

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Author

Paul D. Hanna, Sep 29 2014

Keywords

Comments

Compare to A007840(n) = Sum_{k=0..n} |Stirling1(n, k)|*k!, which equals the number of factorizations of permutations of n letters into ordered cycles.
For n > 1, a(n) is equal to the permanent of the (n-1) X (n-1) matrix in which the (i, j)-entry is equal to delta(i, j) + i, letting delta denote the Kronecker delta function, as illustrated in the below example. - John M. Campbell, Jan 21 2018

Examples

			For example, the (5-1) X (5-1) matrix of the form indicated above is equal to
[2 1 1 1]
[2 3 2 2]
[3 3 4 3]
[4 4 4 5]
and the permanent of the above matrix is equal to 957 = a(5). - _John M. Campbell_, Jan 21 2018
		

Crossrefs

Cf. A008275 (Stirling1 numbers).

Programs

  • Mathematica
    Table[Sum[Abs[StirlingS1[n,k]]*(n-k)!,{k,0,n}],{n,0,20}] (* Vaclav Kotesovec, Sep 30 2014 *)
  • PARI
    {Stirling1(n, k)=if(n==0, 1, n!*polcoeff(binomial(x, n), k))}
    {a(n)=sum(k=0, n, (-1)^(n-k)*Stirling1(n, k)*(n-k)!)}
    for(n=0,20,print1(a(n),", "))

Formula

a(n) ~ ((n-1)!)^2. - Vaclav Kotesovec, Sep 30 2014

A382805 a(n) = Sum_{k=0..n} (-1)^(n-k) * (Stirling1(n,k) * k!)^2.

Original entry on oeis.org

1, 1, 3, 4, -272, -8524, -96596, 9634752, 983055168, 36429411456, -4303305703296, -1051644384152064, -89651253435644160, 10632887072757561600, 5599203549778990667520, 914684633796830925275136, -89559567563652079025946624, -104514775371103880549281775616
Offset: 0

Views

Author

Ilya Gutkovskiy, Apr 05 2025

Keywords

Crossrefs

Programs

  • Mathematica
    Table[Sum[(-1)^(n - k) (StirlingS1[n, k] k!)^2, {k, 0, n}], {n, 0, 17}]
    Table[(n!)^2 SeriesCoefficient[1/(1 + Log[1 + x] Log[1 - y]), {x, 0, n}, {y, 0, n}], {n, 0, 17}]

Formula

a(n) = (n!)^2 * [(x*y)^n] 1 / (1 + log(1 + x) * log(1 - y)).
Previous Showing 101-104 of 104 results.