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 A092590 #19 Jun 09 2024 09:04:43
%S A092590 -1,1,5,8,14,22,25,31,28,48,56,73,78,76,56,80,74,138,112,120,159,136,
%T A092590 102,156,210,185,168,126,240,212,248,212,226,240,226,300,314,283,204,
%U A092590 252,222,474,296,412,339,388,472,360,270,472,378,368,634,396,427,316,404,592,534,628,436,434,582,480,684,456,700,836
%N A092590 a(n) = A065395(A000040(n)); values of commutator of sigma and phi function at prime number arguments.
%C A092590 The sequence differs from A065394 since it is not monotonic.
%H A092590 Amiram Eldar, <a href="/A092590/b092590.txt">Table of n, a(n) for n = 1..10000</a>
%F A092590 a(n) = sigma(prime(n)-1) - phi(prime(n)+1) = A008332(n) - A008331(n). - _Amiram Eldar_, Jun 09 2024
%e A092590 a(1) = sigma(phi(2))- phi(sigma(2)) = sigma(1)-phi(3) = 1-2 = -1.
%t A092590 Table[DivisorSigma[1, p-1] - EulerPhi[p+1], {p, Prime[Range[100]]}] (* _Amiram Eldar_, Jun 09 2024 *)
%o A092590 (Magma) [DivisorSigma(1,EulerPhi(p))-EulerPhi(DivisorSigma(1,p)): p in PrimesUpTo(400)]; // _Bruno Berselli_, Oct 20 2015
%Y A092590 Cf. A000010, A000040, A000203, A033632, A065393, A065394, A065395, A008331, A008332, A092584, A092585, A092586, A092587, A092588, A092589.
%K A092590 sign,look
%O A092590 1,3
%A A092590 _Labos Elemer_, Mar 03 2004