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 A369829 #9 Jun 11 2024 10:17:12 %S A369829 0,1,3,5,9,6,11,4,12,8,18,24,16,29,15,29,17,33,23,42,22,43,63,45,34, %T A369829 59,85,58,30,2,30,61,93,76,52,87,51,14,52,13,53,94,75,54,10,33,79,32, %U A369829 80,31,81,117,189,149,106,161,105,48,21,80,20 %N A369829 a(0) = 0; for n > 0, if n appears in the sequence then a(n) = a(n-1) - sum of indexes where n appeared if that is nonnegative and not already in the sequence, otherwise a(n) = a(n-1) + sum of indexes. Otherwise a(n) = a(n-1) - n if nonnegative and not already in the sequence, otherwise a(n) = a(n-1) + n. %e A369829 a(3) = 5 as a(2) = 3 = n, thus the step size from a(2) is 2. As 1 has previously appeared a(3) = a(2) + 2 = 3 + 2 = 5. %e A369829 a(5) = 6 as a(3) = 5 = n, thus the step size from a(4) is 3. As 6 has not previously appeared a(5) = a(4) - 3 = 9 - 3 = 6. %e A369829 a(29) = 2 as a(13) = 29 = n, and a(15) = 29, 13+15 is 28, thus the step size from a(2) is 28. As 2 has not previously appeared a(29) = a(29) - 28 = 30 - 28 = 2. %Y A369829 Cf. A005132, A340593, A362373. %K A369829 nonn %O A369829 0,3 %A A369829 _Kelvin Voskuijl_, Feb 02 2024