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 A183869 #25 Aug 05 2025 18:10:53
%S A183869 2,4,5,7,8,10,11,12,14,15,16,18,19,20,21,23,24,25,26,28,29,30,31,32,
%T A183869 34,35,36,37,38,40,41,42,43,44,45,47,48,49,50,51,52,54,55,56,57,58,59,
%U A183869 60,62,63,64,65,66,67,68,70,71,72,73,74,75,76,77,79,80,81,82,83,84,85,86,88,89,90,91,92,93,94,95,96,98,99,100,101,102,103,104,105,106,108,109,110,111,112,113,114,115,116,117,119,120
%N A183869 a(n) = n + floor(sqrt(4*n + 5)); complement of A004116.
%C A183869 a(n-2) appears to be the minimum number of rectangular tiles to place on an n X n grid of unit squares, possibly of different sizes, such that each side of every tile lies on a grid line, every unit square is covered by at most one tile, and each row and each column of the grid has exactly one unit square that is not covered by any tile. - _Yifan Xie_, Jul 19 2025 [The conjecture is proven. - _Yifan Xie_, Jul 24 2025]
%H A183869 Art of Problem Solving, <a href="https://artofproblemsolving.com/wiki/index.php/2025_IMO_Problems/Problem_6">2025 IMO Problems/Problem 6</a>
%H A183869 Jinyuan Wang, <a href="/A183869/a183869.pdf">Tiling constructions for a(n-2) on n X n grids, n = 2..16</a>
%t A183869 a=4; b=5; Table[n+Floor[(a*n+b)^(1/2)],{n,0,100}]
%o A183869 (PARI) a(n) = n + sqrtint(4*n+5); \\ _Michel Marcus_, Jul 19 2025
%Y A183869 Cf. A000267, A004116.
%K A183869 nonn,easy
%O A183869 0,1
%A A183869 _Clark Kimberling_, Jan 07 2011