Number of 2-distant 4-noncrossing partitions of {1,...,n}.

Terms

a(0) =1a(1) =1a(2) =2a(3) =5a(4) =15a(5) =52a(6) =203a(7) =877a(8) =4140a(9) =21146a(10) =115938a(11) =677765a(12) =4200011a(13) =27446229a(14) =188255890a(15) =1349652560a(16) =10075332564a(17) =78052115894a(18) =625568350179