a(n) = sum of the numbers between the two n's in A026358.

Terms

a(0) =3a(1) =11a(2) =38a(3) =58a(4) =108a(5) =140a(6) =176a(7) =216a(8) =305a(9) =357a(10) =469a(11) =533a(12) =601a(13) =673a(14) =824a(15) =908a(16) =1082a(17) =1178a(18) =1375a(19) =1483a(20) =1703a(21) =1823a(22) =1947a(23) =2075a(24) =2334a(25) =2474a(26) =2756a(27) =2908a(28) =3064a(29) =3224