a(n) = 2nd elementary symmetric function of the first n+1 odd positive integers.

Terms

a(0) =3a(1) =23a(2) =86a(3) =230a(4) =505a(5) =973a(6) =1708a(7) =2796a(8) =4335a(9) =6435a(10) =9218a(11) =12818a(12) =17381a(13) =23065a(14) =30040a(15) =38488a(16) =48603a(17) =60591a(18) =74670a(19) =91070a(20) =110033a(21) =131813a(22) =156676a(23) =184900a(24) =216775a(25) =252603a(26) =292698a(27) =337386a(28) =387005a(29) =441905