Diagonal sums of A083856.

Terms

a(0) =0a(1) =1a(2) =2a(3) =3a(4) =5a(5) =9a(6) =17a(7) =34a(8) =71a(9) =154a(10) =346a(11) =802a(12) =1914a(13) =4693a(14) =11800a(15) =30379a(16) =79963a(17) =214925a(18) =589223a(19) =1645994a(20) =4681037a(21) =13541446a(22) =39817560a(23) =118925810a(24) =360577616a(25) =1109158545a(26) =3459636358a(27) =10936941299a(28) =35026082521a(29) =113588037953