a(n) = Sum_{j=0..floor(n/2)} (-1)^(j+floor(n/2))*S(2j+q), where S(n) are generalized tribonacci numbers (A001644) and q = (1-(-1)^n)/2.

A074678

a(n) = Sum_{j=0..floor(n/2)} (-1)^(j+floor(n/2))*S(2j+q), where S(n) are generalized tribonacci numbers (A001644) and q = (1-(-1)^n)/2.

Terms

    a(0) =3a(1) =1a(2) =0a(3) =6a(4) =11a(5) =15a(6) =28a(7) =56a(8) =103a(9) =185a(10) =340a(11) =630a(12) =1159a(13) =2127a(14) =3912a(15) =7200a(16) =13243a(17) =24353a(18) =44792a(19) =82390a(20) =151539a(21) =278719a(22) =512644a(23) =942904a(24) =1734271a(25) =3189817a(26) =5866988a(27) =10791078a(28) =19847887a(29) =36505951

External references