a(n) = sum of numbers from 1 to pi(n), where pi(n) = A007955(n).

Terms

a(0) =1a(1) =3a(2) =6a(3) =36a(4) =15a(5) =666a(6) =28a(7) =2080a(8) =378a(9) =5050a(10) =66a(11) =1493856a(12) =91a(13) =19306a(14) =25425a(15) =524800a(16) =153a(17) =17009028a(18) =190a(19) =32004000a(20) =97461a(21) =117370a(22) =276a(23) =55037822976a(24) =7875a(25) =228826a(26) =266085a(27) =240956128a(28) =435a(29) =328050405000