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 A117824 #6 Sep 03 2017 11:27:40
%S A117824 0,1,2,5,4,13,12,19,24,35,50,75,114,177,278,441,704,1129,1816,2927,
%T A117824 4724,7631,12334,19943,32254,52173,84402,136549,220924,357445,578340,
%U A117824 935755,1514064,2449787,3963818,6413571,10377354,16790889,27168206,43959057
%N A117824 a(0) = 0, a(1) = 1; for n >= 2, a(n) = a(n-1) + a(n-2) - (n-1) if that number is positive and not already in the sequence, otherwise a(n) = a(n-1) + a(n-2) + (n-1).
%p A117824 a[0]:=0: a[1]:=1: A:={0,1}: for n from 2 to 42 do if a[n-1]+a[n-2]-n+1>0 and member(a[n-1]+a[n-2]-n+1,A)=false then a[n]:=a[n-1]+a[n-2]-n+1: A:=A union {a[n-1]+a[n-2]-n+1} else a[n]:=a[n-1]+a[n-2]+n-1: A:=A union {a[n-1]+a[n-2]+n-1} fi: od: seq(a[n],n=0..42); # _Emeric Deutsch_, Apr 30 2006
%Y A117824 Cf. A005132, A079053, A117821, A117822, A117823.
%K A117824 nonn,easy
%O A117824 0,3
%A A117824 _N. J. A. Sloane_, Apr 30 2006
%E A117824 More terms from _Emeric Deutsch_, Apr 30 2006