a(n) = A047881(n) / 2.

Terms

a(0) =0a(1) =5a(2) =10a(3) =19a(4) =31a(5) =50a(6) =75a(7) =110a(8) =151a(9) =205a(10) =268a(11) =346a(12) =434a(13) =540a(14) =658a(15) =797a(16) =949a(17) =1124a(18) =1315a(19) =1532a(20) =1765a(21) =2027a(22) =2308a(23) =2620a(24) =2952a(25) =3318a(26) =3706a(27) =4131a(28) =4579a(29) =5066