A129684 - OEIS

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A129684

Exponential Riordan array [1/(1-x^2/2), x].

1, 0, 1, 1, 0, 1, 0, 3, 0, 1, 6, 0, 6, 0, 1, 0, 30, 0, 10, 0, 1, 90, 0, 90, 0, 15, 0, 1, 0, 630, 0, 210, 0, 21, 0, 1, 2520, 0, 2520, 0, 420, 0, 28, 0, 1, 0, 22680, 0, 7560, 0, 756, 0, 36, 0, 1, 113400, 0, 113400, 0, 18900, 0, 1260, 0, 45, 0, 1

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OFFSET

0,8

COMMENTS

Row sums are A087214. Inverse is A129685.

LINKS

Table of n, a(n) for n=0..65.

FORMULA

Number triangle T(n,k) = [k<=n](n!/k!)*(1/2^((n-k)/2))*(1+(-1)^(n-k))/2.

EXAMPLE

Triangle begins

0, 1,

1, 0, 1,

0, 3, 0, 1,

6, 0, 6, 0, 1,

0, 30, 0, 10, 0, 1,

90, 0, 90, 0, 15, 0, 1,

0, 630, 0, 210, 0, 21, 0, 1

MATHEMATICA

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

RiordanArray[1/(1 - #^2/2)&, #&, 11, True] // Flatten (* Jean-François Alcover, Jul 19 2019 *)

CROSSREFS

Cf. A087214, A129685.

Sequence in context: A355172 A102765 A355257 * A247255 A105147 A335262

Adjacent sequences: A129681 A129682 A129683 * A129685 A129686 A129687

KEYWORD

easy,nonn,tabl

AUTHOR

Paul Barry, Apr 28 2007

STATUS

approved