%I #10 Sep 11 2022 00:41:11
%S 2,3,3,5,10,18,31,54,95,167,293,514,902,1583,2778,4875,8555,15013,
%T 26346,46234,81135,142382,249863,438479,769477,1350338,2369678,
%U 4158495,7297650,12806483,22473811,39438789,69210250,121455522,213139583,374033894,656383727,1151873143
%N a(n) = Sum{a(k): k=0,1,2,...,n-3,n-1}; a(n-2) is not a summand; 2 initial terms required.
%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1,1).
%F a(n) = 2*a(n-1) - a(n-2) + a(n-3); 3 initial terms required.
%F G.f.: (2 - x - x^2)/(1 - 2*x + x^2 - x^3). - _Stefano Spezia_, Sep 10 2022
%t LinearRecurrence[{2,-1,1},{2,3,3},38] (* _Stefano Spezia_, Sep 10 2022 *)
%Y Cf. A049856.
%K nonn,easy
%O 0,1
%A _Clark Kimberling_