cp's OEIS Frontend

A190992 Duplicate of A176035.

%I A190992 #17 Aug 29 2025 06:52:56
%S A190992 2,1,5,6,5,6,1,8,9,10,2,3,10,2,6,8,9,13,1,5,10,13,1,4,5,6,10,12,13,14,
%T A190992 6,11,15,18,19,1,2,8,12,13,20,21,22,1,2,11,14,15,17,22,8,9,14,16,18,
%U A190992 25,5,6,7,9,10,13,17,18,19,21,22,23,25,1,10,12,22,24,28,29,3,6,9,11,18,22,31,2
%N A190992 Duplicate of A176035.
%C A190992 Previous name was: Square excess of squarefree semiprimes.
%H A190992 G. C. Greubel, <a href="/A190992/b190992.txt">Table of n, a(n) for n = 1..5000</a>
%t A190992 A006881=Sort@Flatten@Table[Prime[m]*Prime[n],{n,2,150},{m,n-1}];
%t A190992 Table[A006881[[n]]-Floor[Sqrt[A006881[[n]]]]^2, {n,100}]
%o A190992 (Magma)
%o A190992 A006881:= [n: n in [1..1000] | EulerPhi(n) + DivisorSigma(1, n) eq 2*(n+1)];
%o A190992 [A006881[n] - Floor(Sqrt(A006881[n]))^2: n in [1..100]]; // _G. C. Greubel_, Oct 26 2022
%o A190992 (SageMath)
%o A190992 A006881=[n for n in (1..750) if euler_phi(n) + sigma(n,1) == 2*n+2]
%o A190992 [A006881[n] - isqrt(A006881[n])^2 for n in range(101)] # _G. C. Greubel_, Oct 26 2022
%K A190992 dead
%O A190992 1,1
%A A190992 _Vladimir Joseph Stephan Orlovsky_, Jun 02 2011
%E A190992 Data corrected by _G. C. Greubel_, Oct 26 2022
%E A190992 Marked as duplicate by _R. J. Mathar_, Aug 25 2025