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

Terms

a(0) =0a(1) =0a(2) =2a(3) =3a(4) =12a(5) =23a(6) =58a(7) =123a(8) =266a(9) =557a(10) =1168a(11) =2400a(12) =4911a(13) =9982a(14) =20196a(15) =40643a(16) =81499a(17) =162899a(18) =324678a(19) =645404a(20) =1280042a(21) =2533565a(22) =5005449a(23) =9872464a(24) =19442206a(25) =38234945a(26) =75096856a(27) =147324049a(28) =288705896a(29) =565201569