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 A111653 #13 Sep 07 2025 00:02:55 %S A111653 4,6,6,8,8,8,9,9,9,9,10,10,10,10,10,12,12,12,12,12,12,14,14,14,14,14, %T A111653 14,14,15,15,15,15,15,15,15,15,16,16,16,16,16,16,16,16,16,18,18,18,18, %U A111653 18,18,18,18,18,18,20,20,20,20,20,20,20,20,20,20,20,21,21,21,21,21,21,21 %N A111653 n-th composite number appears n times. %C A111653 A002808(n) appears n times. %o A111653 (Python) %o A111653 from math import isqrt %o A111653 from sympy import composite %o A111653 def A111653(n): return composite(isqrt(n<<3)+1>>1) # _Chai Wah Wu_, Sep 06 2025 %Y A111653 Cf. A002808, A111654, A111655. %K A111653 easy,less,nonn,changed %O A111653 1,1 %A A111653 _Jonathan Vos Post_, Aug 12 2005