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A129684
Exponential Riordan array [1/(1-x^2/2), x].
2
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
OFFSET
0,8
COMMENTS
Row sums are A087214. Inverse is A129685.
FORMULA
Number triangle T(n,k) = [k<=n](n!/k!)*(1/2^((n-k)/2))*(1+(-1)^(n-k))/2.
EXAMPLE
Triangle begins
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
MATHEMATICA
(* The function RiordanArray is defined in A256893. *)
RiordanArray[1/(1 - #^2/2)&, #&, 11, True] // Flatten (* Jean-François Alcover, Jul 19 2019 *)
CROSSREFS
Sequence in context: A355172 A102765 A355257 * A247255 A105147 A335262
KEYWORD
easy,nonn,tabl
AUTHOR
Paul Barry, Apr 28 2007
STATUS
approved