a(n) = 4*Sum_{i=0..n-1} C(2*i+1, i)*C(n-1, n-1-i)*(-1)^(n-1-i)*2^i for n > 0, a(0) = 1.
A085458
a(n) = 4*Sum_{i=0..n-1} C(2*i+1, i)*C(n-1, n-1-i)*(-1)^(n-1-i)*2^i for n > 0, a(0) = 1.
Terms
- a(0) =1a(1) =4a(2) =20a(3) =116a(4) =708a(5) =4452a(6) =28532a(7) =185300a(8) =1215268a(9) =8030404a(10) =53381844a(11) =356577588a(12) =2391430020a(13) =16092704292a(14) =108605848116a(15) =734783381652
External references
- oeis: A085458