Number of 3's in partitions of n into distinct parts.

Terms

a(0) =0a(1) =0a(2) =1a(3) =1a(4) =1a(5) =1a(6) =1a(7) =2a(8) =3a(9) =4a(10) =4a(11) =5a(12) =6a(13) =8a(14) =10a(15) =12a(16) =14a(17) =17a(18) =20a(19) =24a(20) =29a(21) =34a(22) =40a(23) =47a(24) =55a(25) =64a(26) =75a(27) =87a(28) =101a(29) =117