Alternating sum of the Fibonacci numbers multiplied by their (combinatorial) indices.

Terms

a(0) =0a(1) =1a(2) =3a(3) =6a(4) =14a(5) =26a(6) =52a(7) =95a(8) =177a(9) =318a(10) =572a(11) =1012a(12) =1784a(13) =3117a(14) =5423a(15) =9382a(16) =16170a(17) =27758a(18) =47500a(19) =81035a(20) =137885a(21) =234046a(22) =396408a(23) =670056a(24) =1130544a(25) =1904281a(26) =3202587a(27) =5378310a(28) =9020102a(29) =15109058