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 A376745 #14 Oct 07 2024 09:07:10
%S A376745 2,3,4,5,7,8,9,10,11,12,13,14,15,16,17,19,20,21,22,23,24,25,26,27,28,
%T A376745 29,30,31,32,33,34,35,36,37,38,39,41,42,43,44,45,46,47,48,49,50,51,52,
%U A376745 53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71
%N A376745 Numbers that are not pentagonal pyramidal numbers.
%C A376745 Complement of A002411. Numbers not of the form k^2*(k+1)/2.
%H A376745 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PentagonalPyramidalNumber.html">Pentagonal Pyramidal Number</a>
%F A376745 a(n) = n+m if 2n>m(m-1)(m+2) and a(n) = n+m-1 otherwise where m = floor((2n)^(1/3)).
%t A376745 p=71;l=Floor[(2p)^(1/3)];Complement[Range[p],Table[n^2 (n + 1)/2, {n, 0, l}]] (* _James C. McMahon_, Oct 07 2024 *)
%o A376745 (Python)
%o A376745 from sympy import integer_nthroot
%o A376745 def A376745(n): return n+(m:=integer_nthroot(k:=n<<1,3)[0])-(k<=m*(m-1)*(m+2))
%Y A376745 Cf. A002411, A000330, A000537, A302058, A376573.
%K A376745 nonn,easy
%O A376745 1,1
%A A376745 _Chai Wah Wu_, Oct 03 2024