Partial sums of (1/2)*floor(7^n/10).

Terms

a(0) =0a(1) =2a(2) =19a(3) =139a(4) =979a(5) =6861a(6) =48038a(7) =336278a(8) =2353958a(9) =16477720a(10) =115344057a(11) =807408417a(12) =5651858937a(13) =39563012579a(14) =276941088076