Partial sums of A000141.

Terms

a(0) =1a(1) =13a(2) =73a(3) =233a(4) =485a(5) =797a(6) =1341a(7) =2301a(8) =3321a(9) =4197a(10) =5757a(11) =8157a(12) =10237a(13) =12277a(14) =15541a(15) =19701a(16) =23793a(17) =27273a(18) =31653a(19) =38853a(20) =45405a(21) =50013a(22) =58173a(23) =68733a(24) =76957a(25) =84769a(26) =94969a(27) =108089a(28) =120569a(29) =130673