Number of compositions of n with the multiplicity of the first part odd.

Terms

a(0) =1a(1) =1a(2) =4a(3) =4a(4) =12a(5) =18a(6) =44a(7) =72a(8) =158a(9) =288a(10) =604a(11) =1146a(12) =2332a(13) =4528a(14) =9126a(15) =17944a(16) =35940a(17) =71130a(18) =142132a(19) =282344a(20) =563630a(21) =1121936a(22) =2239060a(23) =4462530a(24) =8906236a(25) =17764160a(26) =35458774a(27) =70761520a(28) =141272876a(29) =282025466