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A100630 Array read by antidiagonals: T(m,n) = Sum(1<=i<=m) [ i*(n-1+i)! ] 2
1, 2, 5, 6, 14, 23, 24, 54, 86, 119, 120, 264, 414, 566, 719, 720, 1560, 2424, 3294, 4166, 5039, 5040, 10800, 16680, 22584, 28494, 34406, 40319, 40320, 85680, 131760, 177960, 224184, 270414, 316646, 362879, 362880, 766080, 1174320, 1583280 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Inversion vector corresponding to T(m,n): ( n zeros , 1,2,3,...,m , zeros... )

These are the numbers of permutations (in reverse colexicographical order, compare A055089) that reverse a set of consecutive elements and leave all other elements unchanged. Permutation A(m,n) reverses all elements from n to m+n.

The former title of this sequence refers to finite tables of permutations in lexicographical order: "Triangle read by rows: row n gives the index number in the tables of permutations of order n+1, n+2, ... of the permutation in which the first n items are reversed and the remaining items are in order."

LINKS

Tilman Piesk, Table of n, a(n) for n = 1..2016

Tilman Piesk, Inversion (discrete mathematics) (Wikiversity)

EXAMPLE

T(3,2) = Sum( 1 <= i <= 3 ) [ i * (1+i)! ]

= 1*(1+1)! + 2*(1+2)! + 3*(1+3)!

= 1*2 + 2*6 + 3*24

= 86

PROG

MATLAB code is shown on the Wikiversity page.

Using Iverson's J language, A. p for a permutation p gives the row number in the table of permutations of order (length of p) which has p as its value. For example, q 0 4 9 6 7 5 1 11 8 10 2 3 A. q 13610272.

CROSSREFS

See A100711 for another version. Row 2 is A052649.

Sequence in context: A211369 A006596 A000092 * A057302 A237352 A109784

Adjacent sequences:  A100627 A100628 A100629 * A100631 A100632 A100633

KEYWORD

easy,nonn,tabl

AUTHOR

Eugene McDonnell (eemcd(AT)mac.com), Dec 03 2004

EXTENSIONS

Rewritten by Tilman Piesk, Jul 13 2012

STATUS

approved

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Last modified December 22 07:03 EST 2014. Contains 252328 sequences.