Partial sums of A080674.

Terms

a(0) =4a(1) =24a(2) =108a(3) =448a(4) =1812a(5) =7272a(6) =29116a(7) =116496a(8) =466020a(9) =1864120a(10) =7456524a(11) =29826144a(12) =119304628a(13) =477218568a(14) =1908874332a(15) =7635497392a(16) =30541989636a(17) =122167958616a(18) =488671834540