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 A183223 #11 Oct 07 2024 01:18:36
%S A183223 2,3,4,5,6,7,8,9,10,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,
%T A183223 28,29,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,
%U A183223 52,53,54,55,56,57,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,96,97,98,99,100,101,102
%N A183223 Complement of the 11-gonal numbers.
%F A183223 a(n) = n + floor(1/2+(2n/9+2/9)^(1/2)).
%t A183223 Table[n+Floor[1/2+(2n/9+2/9)^(1/2)], {n,100}]
%o A183223 (Python)
%o A183223 from math import isqrt
%o A183223 def A183223(n): return n+(isqrt((n<<3|4)//9)+1>>1) # _Chai Wah Wu_, Oct 06 2024
%Y A183223 Cf. A051682 (11-gonal numbers).
%K A183223 nonn
%O A183223 1,1
%A A183223 _Clark Kimberling_, Jan 01 2011