Number of reversible strings with n beads of 5 colors.

Terms

a(0) =1a(1) =5a(2) =15a(3) =75a(4) =325a(5) =1625a(6) =7875a(7) =39375a(8) =195625a(9) =978125a(10) =4884375a(11) =24421875a(12) =122078125a(13) =610390625a(14) =3051796875a(15) =15258984375a(16) =76294140625a(17) =381470703125