G.f.: A(x) = Sum_{n>=0} x^n * (1+x)^A038722(n), where A038722(n) = floor(sqrt(2*n)+1/2)^2 - n + 1.

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =6a(5) =9a(6) =21a(7) =35a(8) =42a(9) =70a(10) =168a(11) =330a(12) =471a(13) =561a(14) =855a(15) =1950a(16) =4402a(17) =8023a(18) =11616a(19) =14245a(20) =18425a(21) =33880a(22) =78519a(23) =172047a(24) =320451a(25) =500579a(26) =668582a(27) =819819a(28) =1113658a(29) =2046760