seq? Least k such that the length of the Roman numeral for k = the length of the binary representation of k = n

[Jonathan Post]

I'm sorry; I missed the n=5 case by typing error.

1, 2, 7, 8, 18, 33, 78, 138, 278, 688, 1288

n a(n) because
1   1   I = 1_2
2   2   II = 10_2
3   7   VII = 111_2
4   8   VIII = 1000_2
5   18  XVIII = 10010_2
6   33   XXXIII = 100001_2
7   78   LXXVIII = 1001110_2
8  138   CXXXVIII = 10001010_2
9  278   CCLXXVIII = 100010110_2
10 688   DCLXXXVIII = 1010110000_2
11 1288  MCCLXXXVIII = 10100001000_2


On 7/5/08, Jonathan Post <jvospost3 at gmail.com> wrote:
> Okay, here's another weird one relating Roman numerals to a base.
>
>  1, 2, 7, 8, 33, 78, 138, 278, 688, 1288
>
>  Least k such that the length of the Roman numeral for k = the length
>  of the binary representation of k = n.
>
>  a(n) = MIN{k such that A006968(k) = A070939(k) = n}
>
>  Cf. A036787, A007088, A006968, A070939
>