OFFSET
0,2
COMMENTS
Hankel transform of abs(A002420) (which is 2*0^n - binomial(2n,n)/(2n-1)).
LINKS
FORMULA
G.f.: (1-6x)/(1-2x)^2;
a(n) = Sum_{k=0..n} A121314(n,k)*(-1)^k*2^(3n-2k). - Philippe Deléham, Oct 31 2008
From Amiram Eldar, Oct 01 2022: (Start)
Sum_{n>=0} 1/a(n) = 1 - arcsinh(1)/sqrt(2).
Sum_{n>=0} (-1)^n/a(n) = 1 + arctan(1/sqrt(2))/sqrt(2). (End)
MATHEMATICA
a[n_] := (1-2n)*2^n; Array[a, 40, 0] (* Amiram Eldar, Oct 01 2022 *)
CROSSREFS
KEYWORD
easy,sign
AUTHOR
Paul Barry, Jul 26 2008
STATUS
approved