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 A069861 #4 Dec 05 2013 19:55:18
%S A069861 1,2,3,5,6,9,10,11,12,15,18,20,21,22,25,27,30,33,36,39,42,44,45,50,54,
%T A069861 56,60,68,72,75,90,98,100,104,108,110,111,114,120,125,126,130,132,135,
%U A069861 140,148,150,154,155,156,162,168,180,182,185,196,198,200,205,210,216
%N A069861 Numbers n that divide the concatenation of next n numbers.
%e A069861 9 divides 101112131415161718 hence is a member.
%t A069861 f[n_] := Block[{j = 0, k = n + 1}, While[k < 2n + 1, j = ToExpression[ StringJoin[ ToString[j], ToString[k]]]; k++ ]; j]; Select[ Range[300], IntegerQ[ f[ # ] / # ] & ]
%Y A069861 Cf. A069860, A069862.
%K A069861 base,nonn
%O A069861 1,2
%A A069861 _Amarnath Murthy_, Apr 18 2002
%E A069861 Edited, corrected and extended by _Robert G. Wilson v_