
EXAMPLE

There are nine onedigit numbers divisible by 1 so a(1)=9. For 2digit numbers, the second digit must make it divisible by 2^2 which gives 22 numbers: 12, 16, 20, 24, 28, 32, 36, 40, 44, 48, 52, 56, 60, 64, 68, 72, 76, 80, 84, 88, 92, 96 to satisfy the requirement. So a(2)=22.


MATHEMATICA

a = Table[j, {j, 9}]; r = 2; t = {}; While[! a == {}, n = Length[a]; k = 1; b = {}; While[! k > n, z0 = a[[k]]; Do[z = 10*z0 + j; If[Mod[z, r*r] == 0, b = Append[b, z]], {j, 0, 9}]; k++]; AppendTo[t, n]; a = b; r++]; t
