%I #5 May 19 2013 12:18:42
%S 1,4,9,21,24,34,56,66,92,100,112,117,135,180,260,349,387,393,411,574,
%T 617,787,1209
%N Difference between last prime < 10^n and 10^n is a record high.
%e For a(19)=411, the difference is 4433 and no other n <= 540 exceeds that difference.
%t PrevPrim[n_] := Block[{k = n - 1}, While[ !PrimeQ[k], k-- ]; k]; d = 0; k = 1; Do[ While[f = 10^k - PrevPrim[10^k]; d >= f, k++ ]; d = f; Print[k], {n, 1, 50}]
%Y Cf. A033874.
%K base,nonn
%O 1,2
%A _Jeff Burch_
%E Edited and extended by _Robert G. Wilson v_, Jun 18 2002
%E a(23) from _Robert G. Wilson v_, Jan 10 2007