An accelerator sequence for Catalan's constant.

Terms

a(0) =5a(1) =-1a(2) =9a(3) =-4a(4) =25a(5) =-16a(6) =78a(7) =-64a(8) =257a(9) =-256a(10) =874a(11) =-1013a(12) =3034a(13) =-3953a(14) =10684a(15) =-15229a(16) =38017a(17) =-58056a(18) =136338a(19) =-219508a(20) =491870a(21) =-824737a(22) =1782735a(23) =-3083887a(24) =6484514a(25) =-11489516a(26) =23652443a(27) =-42688039a(28) =86459608a(29) =-158270401