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A122833 Exponential Riordan array (e^(-x(1+x)),x). 1
1, -1, 1, -1, -2, 1, 5, -3, -3, 1, 1, 20, -6, -4, 1, -41, 5, 50, -10, -5, 1, 31, -246, 15, 100, -15, -6, 1, 461, 217, -861, 35, 175, -21, -7, 1, -895, 3688, 868, -2296, 70, 280, -28, -8, 1 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

0,5

COMMENTS

Inverse of A122832. Row sums are (-1)^(n/2)(1+(-1)^n)(n)!/(2(n/2)!).

LINKS

Table of n, a(n) for n=0..44.

FORMULA

Number triangle T(n,k)=(n!/k!)sum{i=0..n-k, (-1)^i*C(i,n-k-i)/i!}

EXAMPLE

Triangle begins

1,

-1, 1,

-1, -2, 1,

5, -3, -3, 1,

1, 20, -6, -4, 1,

-41, 5, 50, -10, -5, 1

MATHEMATICA

(* The function RiordanArray is defined in A256893. *)

RiordanArray[E^(-# (1 + #))&, #&, 9, True] // Flatten (* Jean-Fran├žois Alcover, Jul 19 2019 *)

CROSSREFS

Cf. A122832.

Sequence in context: A106534 A123346 A163840 * A193692 A075303 A076062

Adjacent sequences:  A122830 A122831 A122832 * A122834 A122835 A122836

KEYWORD

easy,sign,tabl

AUTHOR

Paul Barry, Sep 12 2006

STATUS

approved

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Last modified May 16 11:09 EDT 2021. Contains 343942 sequences. (Running on oeis4.)