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 A377306 #15 Oct 28 2024 06:13:17 %S A377306 2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,18,19,20,21,22,23,24,25,26,27, %T A377306 28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50, %U A377306 51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69 %N A377306 Numbers that are not the sum of the first k fourth powers. %C A377306 Complement of A000538. %F A377306 a(n) = n+m if 30n > m(m-1)(6m^3+21m^2+31m+31) and a(n) = n+m-1 otherwise, where m = floor((5n)^(1/5)). %t A377306 lim=69;l4=Ceiling[lim^(1/4)];Complement[Range[lim],Accumulate[Range[0, l4]^4]] (* _James C. McMahon_, Oct 24 2024 *) %o A377306 (Python) %o A377306 from sympy import integer_nthroot %o A377306 def A377306(n): return n+(m:=integer_nthroot(5*n,5)[0])-(30*n<=m*(m-1)*(m*(m*(3*((m<<1)+7))+31)+31)) %Y A377306 Cf. A133137, A000330, A000537, A302058, A376573, A000538, A376745. %K A377306 nonn,easy %O A377306 1,1 %A A377306 _Chai Wah Wu_, Oct 23 2024