(n-2)nd Catalan number is congruent to n/3 mod n.

Terms

a(0) =3a(1) =6a(2) =36a(3) =39a(4) =42a(5) =90a(6) =93a(7) =96a(8) =108a(9) =111a(10) =114a(11) =252a(12) =255a(13) =258a(14) =270a(15) =273a(16) =276a(17) =324a(18) =327a(19) =330a(20) =360a(21) =363a(22) =366a(23) =738a(24) =741a(25) =744a(26) =756a(27) =759a(28) =762a(29) =810