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 A052511 #15 Mar 26 2025 20:22:52 %S A052511 0,-1,-1,-2,0,-2,0,-2,-1,1,1,1,3,1,1,2,6,2,6,4,2,4,6,4,9,9,7,5,5,1,13, %T A052511 11,13,11,17,10,14,16,16,14,18,12,20,16,14,12,22,24,25,21,21,21,21,23, %U A052511 25,23,25,23,27,19,19,25,33,30,28,24,36,36,42,36,38,32,38,40,40,38,40,40,42,40,45,43 %N A052511 a(n) = prime(n) - 1 - A006218(n). %C A052511 a(n) > 0 for n >= 10. %C A052511 The old entry with this sequence number was a duplicate of A052509. %H A052511 David Applegate and N. J. A. Sloane, <a href="/A052511/b052511.txt">Table of n, a(n) for n = 1..1000</a> %o A052511 (Python) %o A052511 from math import isqrt %o A052511 from sympy import prime %o A052511 def A052511(n): return prime(n)-1+(s:=isqrt(n))**2-(sum(n//k for k in range(1,s+1))<<1) # _Chai Wah Wu_, Mar 26 2025 %Y A052511 See A088526 for another version. %K A052511 sign %O A052511 1,4 %A A052511 _David Applegate_ and _N. J. A. Sloane_, Oct 14 2008