Number of Dyck n-paths with ascents and descents of length equal to 1 (mod 4).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =2a(6) =4a(7) =7a(8) =11a(9) =17a(10) =28a(11) =49a(12) =87a(13) =152a(14) =262a(15) =453a(16) =794a(17) =1408a(18) =2507a(19) =4462a(20) =7943a(21) =14179a(22) =25415a(23) =45713a(24) =82398a(25) =148731a(26) =268859a(27) =486890a(28) =883411a(29) =1605582