"Correlation triangle" of central binomial coefficients A000984.

Terms

a(0) =1a(1) =2a(2) =2a(3) =6a(4) =5a(5) =6a(6) =20a(7) =14a(8) =14a(9) =20a(10) =70a(11) =46a(12) =41a(13) =46a(14) =70a(15) =252a(16) =160a(17) =134a(18) =134a(19) =160a(20) =252a(21) =924a(22) =574a(23) =466a(24) =441a(25) =466a(26) =574a(27) =924a(28) =3432a(29) =2100