A001333(n), n >= 1, convolved with itself.

Terms

a(0) =1a(1) =6a(2) =23a(3) =76a(4) =233a(5) =682a(6) =1935a(7) =5368a(8) =14641a(9) =39406a(10) =104935a(11) =276996a(12) =725849a(13) =1890258a(14) =4896415a(15) =12624752a(16) =32419297a(17) =82951766a(18) =211573047a(19) =538086716a(20) =1364974409a(21) =3454480250a(22) =8724052271a(23) =21989264232a(24) =55326056977a(25) =138975010110