The female of a pair of recurrences.

Terms

a(0) =1a(1) =1a(2) =2a(3) =2a(4) =3a(5) =3a(6) =4a(7) =5a(8) =5a(9) =6a(10) =6a(11) =7a(12) =8a(13) =8a(14) =9a(15) =9a(16) =10a(17) =11a(18) =11a(19) =12a(20) =13a(21) =13a(22) =14a(23) =14a(24) =15a(25) =16a(26) =16a(27) =17a(28) =17a(29) =18