Number of permutations of n elements divided by the number of quaternary heaps on n+1 elements.

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =2a(6) =3a(7) =4a(8) =5a(9) =10a(10) =15a(11) =20a(12) =25a(13) =50a(14) =75a(15) =100a(16) =125a(17) =250a(18) =375a(19) =500a(20) =625a(21) =1500a(22) =2625a(23) =4000a(24) =5625a(25) =12500a(26) =20625a(27) =30000a(28) =40625a(29) =87500