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 A178891 #6 Aug 02 2015 12:52:09
%S A178891 0,5,10,15,20,21,30,31,40,45,42,47,60,61,62,63,80,85,90,95,84,85,94,
%T A178891 95,120,125,122,127,124,125,126,127,160,165,170,175,180,181,190,191,
%U A178891 168,173,170,175,188,189,190,191,240,245,250,255,244,245,254,255,248,253
%N A178891 a(n) = n OR 4n, where OR is bitwise OR.
%C A178891 Perhaps this is a rearrangement of A115772?
%p A178891 read("transforms") ; for n from 0 to 120 do printf("%d,", ORnos(n,4*n) ) ; end do: # _R. J. Mathar_, Jun 26 2010
%t A178891 f[n_] := BitOr[n, 4n]; Array[f, 58, 0] (* _Robert G. Wilson v_, Jun 28 2010 *)
%Y A178891 Cf. A163617, A178890, A178892, A178893, A178894, A178895, A178896, A178897.
%K A178891 nonn
%O A178891 0,2
%A A178891 _Dmitry Kamenetsky_, Jun 21 2010
%E A178891 More terms from _R. J. Mathar_ and _Robert G. Wilson v_, Jun 26 2010