数列 a [ k ] は

a [ k ] = ( 1 / 7 ) * ( 7 / 6 ) ^ k ( 1 ≦ k ≦ 6 )

a [ k + 6 ]
= ( 1 / 6 ) * ( a [ k + 5 ] + a [ k + 4 ] + ･ ･ ･ + a [ k ] ) ( 1 ≦ k )

を満たすとき

0.285 < a [ 2010 ] < 0.286