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 A075003 #5 Dec 05 2013 19:55:34 %S A075003 5,10,16,21,27,32,38,43,49,54,555,605,656,706,757,807,858,908,959, %T A075003 1009,1060,1110,1161,1211,1262,1312,1363,1413,1464,1514,1565,1615, %U A075003 1666,1716,1767,1817,1868,1918,1969,2019,2070,2120,2171,2221,2272,2322,2373,2423 %N A075003 Floor[ concatenation of n+1 and n divided by 2 ]. %e A075003 Sequence exhibits similar properties to A074993. %p A075003 seq(floor((n*10+(n-1))/2),n=1..10),seq(floor((n*100+(n-1))/2),n=11..99); %Y A075003 Cf. A074991 to A075000 and A075004 to A075010. %K A075003 base,nonn %O A075003 0,1 %A A075003 _Amarnath Murthy_, Sep 01 2002 %E A075003 More terms from _Sascha Kurz_, Jan 14 2003