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 A308045 #13 May 15 2019 04:52:06 %S A308045 1,2,3,4,35,44,111,123,1105,1900,2920,12452,17889,34200,65067,716148, %T A308045 14134055,179040201,221709100,221743300,221766100,221788900, %U A308045 1120968741,1272582040,1441454511,7339101375 %N A308045 Numbers k such that usigma(k) = round(zeta(2)/zeta(3)*k), where usigma(k) is the sum of unitary divisors of k (A034448). %C A308045 The unitary version of A072355. %C A308045 zeta(2)/zeta(3) is the asymptotic mean of the unitary abundancy index usigma(k)/k (A306633). %C A308045 a(27) > 10^10. %e A308045 35 is in the sequence since usigma(35) = 48, and (zeta(2)/zeta(3)) * 35 = 47.895... has a round value of 48. %t A308045 usigma[1] = 1; usigma[n_] := Times @@ (1 + Power @@@ FactorInteger[n]); meanAb = Zeta[2]/Zeta[3]; Select[Range[10^6], usigma[#] == Round[meanAb*#] &] %Y A308045 Cf. A002117, A013661, A034448, A072355, A074920, A306633. %K A308045 nonn,more %O A308045 1,2 %A A308045 _Amiram Eldar_, May 10 2019