This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A089298 #6 Mar 14 2015 17:54:23
%S A089298 11,251,14551,155581,4545551,45555581,555555881,44555555581,
%T A089298 455555558581,5555555888551,255555555585881,14555555558558851,
%U A089298 155555555858885551,2555555555558885851,45555555555585855881
%N A089298 Smallest prime with digit product 10^n.
%C A089298 These numbers may not contain the digits {0, 3, 6, 7 or 9} and must end with the digit 1. Also the number of 2's plus half the number of 4's plus a quarter of the number of 8's must equal the number of 5's which in turn must equal n. - _Robert G. Wilson v_, Nov 06 2003
%e A089298 a(4) = 4545551 and the digit product = 10^4.
%t A089298 NextPrim[n_] := Block[{k = n + 1}, While[ !PrimeQ[k], k++ ]; k]; a = Table[0, {10}]; p = 2; Do[ q = Log[10, Times @@ IntegerDigits[p]]; If[q != 0 && IntegerQ[q] && a[[q]] == 0, a[[q]] = p; Print[q, " = ", p]]; p = NextPrim[p], {n, 1, 10^9}]; a
%Y A089298 Cf. A089365, A088653, A090840, A091465, A090841.
%K A089298 base,nonn
%O A089298 0,1
%A A089298 _Amarnath Murthy_, Oct 30 2003
%E A089298 Edited, corrected and extended by _Robert G. Wilson v_, Nov 06 2003