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 A058208 #11 Apr 23 2024 08:29:02 %S A058208 -1,-2,-1,-3,0,-4,3,-2,3,1,10,-3,14,7,11,7,24,7,30,12,26,26,43,11,44, %T A058208 38,45,34,64,27,72,47,67,66,77,40,98,82,92,63,117,69,127,93,105,117, %U A058208 147,78,151,121,149,129,180,121,175,134,181,178,215,114,227,200 %N A058208 a(n) = floor(6*n*sqrt(n)/Pi^2) - sigma(n), where sigma(n) is the sum of the divisors of n (A000203). %C A058208 Always > 0 for n > 12. %D A058208 József Sándor, Dragoslav S. Mitrinovic, and Borislav Crstici, Handbook of Number Theory I, Springer Science & Business Media, 2005, Chapter III, p. 77, section III.1.1.c. %t A058208 a[n_] := Floor[n * Sqrt[n] / Zeta[2]] - DivisorSigma[1, n]; Array[a, 100] (* _Amiram Eldar_, Apr 23 2024 *) %o A058208 (PARI) a(n)=6*n*sqrt(n)\Pi^2 - sigma(n) \\ _Charles R Greathouse IV_, Feb 14 2013 %Y A058208 Cf. A000203, A057641, A055682, A059956. %K A058208 sign %O A058208 1,2 %A A058208 _N. J. A. Sloane_, Nov 29 2000