The number of quinary strings of length n containing 00.

Terms

a(0) =0a(1) =0a(2) =1a(3) =9a(4) =65a(5) =421a(6) =2569a(7) =15085a(8) =86241a(9) =483429a(10) =2669305a(11) =14564061a(12) =78699089a(13) =421880725a(14) =2246459881a(15) =11894065549a(16) =62665617345a(17) =328756309701