An accelerator sequence for Catalan's constant.

Terms

a(0) =4a(1) =1a(2) =7a(3) =4a(4) =19a(5) =16a(6) =58a(7) =64a(8) =187a(9) =247a(10) =622a(11) =925a(12) =2110a(13) =3394a(14) =7252a(15) =12289a(16) =25147a(17) =44116a(18) =87727a(19) =157492a(20) =307294a(21) =560200a(22) =1079371a(23) =1987891a(24) =3798310a(25) =7043041a(26) =13382818a(27) =24927430a(28) =47191492a(29) =88165105