Number of parts in all partitions of n in which no part occurs more than twice.

Terms

a(0) =0a(1) =1a(2) =3a(3) =3a(4) =8a(5) =11a(6) =17a(7) =23a(8) =36a(9) =48a(10) =69a(11) =88a(12) =125a(13) =157a(14) =212a(15) =271a(16) =356a(17) =445a(18) =574a(19) =711a(20) =906a(21) =1118a(22) =1400a(23) =1711a(24) =2125a(25) =2583a(26) =3171a(27) =3828a(28) =4666a(29) =5604