a(n) = A045820(n)/2.

Terms

a(0) =1a(1) =12a(2) =62a(3) =184a(4) =373a(5) =644a(6) =1110a(7) =1768a(8) =2482a(9) =3452a(10) =4768a(11) =6056a(12) =7815a(13) =10296a(14) =12294a(15) =14816a(16) =18736a(17) =21648a(18) =25246a(19) =30728a(20) =34362a(21) =39780a(22) =47702a(23) =52176a(24) =59113a(25) =68696a(26) =74318a(27) =83960a(28) =95952a(29) =102356