Sum of the middle parts in the partitions of 4n-1 into 3 parts.

Terms

a(0) =1a(1) =8a(2) =31a(3) =80a(4) =159a(5) =282a(6) =459a(7) =690a(8) =993a(9) =1378a(10) =1841a(11) =2404a(12) =3077a(13) =3852a(14) =4755a(15) =5796a(16) =6963a(17) =8286a(18) =9775a(19) =11414a(20) =13237a(21) =15254a(22) =17445a(23) =19848a(24) =22473a(25) =25296a(26) =28359a(27) =31672a(28) =35207a(29) =39010