Number of compositions of n where the difference between largest and smallest parts equals four.

Terms

a(0) =0a(1) =0a(2) =2a(3) =3a(4) =12a(5) =23a(6) =61a(7) =132a(8) =294a(9) =639a(10) =1377a(11) =2922a(12) =6178a(13) =12953a(14) =27021a(15) =56106a(16) =116030a(17) =239090a(18) =491202a(19) =1006361a(20) =2056755a(21) =4194230a(22) =8536023a(23) =17340787a(24) =35168957a(25) =71217347a(26) =144012394a(27) =290835635a(28) =586637532a(29) =1181960546