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 A119426 #3 Mar 30 2012 17:36:44 %S A119426 123,135,147,159,234,246,258,345,357,369,456,468,567,579,678,789,1234, %T A119426 1357,1611,1713,1815,1917,2345,2468,2610,2712,2814,2916,3456,3579, %U A119426 3711,3813,3915,4567,4710,4812,4914,5678,5811,5913,6789,6810,6912,7911,8910 %N A119426 Concatenation of 3 or more numbers in arithmetic progression with positive common difference. %C A119426 Leading zeros are not permitted. This sequence, A119427 and the three-digit and larger terms of A010785 are subsequences of A034840. %e A119426 159 is the concatenation of 1, 5 and 9, which have common difference (c.d.) 4. %e A119426 The term 12345, the concatenation of 1, 2, 3, 4 and 5 (c.d. 1), is also the concatenation of 1, 23 and 45 (with c.d. 22). %Y A119426 Cf. A119427, A010785, A034840. %K A119426 base,nonn %O A119426 0,1 %A A119426 _Rick L. Shepherd_, May 22 2006