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 A351561 #18 Jul 21 2025 09:44:01
%S A351561 1,3,3,5,3,8,3,8,6,10,3,14,3,12,11,13,3,18,3,18,13,16,3,24,8,18,13,22,
%T A351561 3,30,3,22,17,22,15,33,3,24,19,32,3,38,3,30,27,28,3,42,10,36,23,34,3,
%U A351561 44,19,40,25,34,3,56,3,36,33,39,21,54,3,42,29,54,3,60,3,42,41,46,21,62,3,58,32,46,3,72,25,48
%N A351561 a(n) = n + d(n) - phi(n), where d is the number of divisors function, and phi is the Euler totient function.
%H A351561 Antti Karttunen, <a href="/A351561/b351561.txt">Table of n, a(n) for n = 1..20000</a>
%F A351561 a(n) = A000005(n) + A051953(n) = n - A063070(n) = n + A000005(n) - A000010(n).
%F A351561 a(n) = Sum_{d|n} (1 + phi(d) - d*mu(n/d)). - _Wesley Ivan Hurt_, Jul 21 2025
%t A351561 Array[# + DivisorSigma[0, #] - EulerPhi[#] &, 86] (* _Michael De Vlieger_, Feb 21 2022 *)
%o A351561 (PARI) A351561(n) = (n+numdiv(n)-eulerphi(n));
%Y A351561 Cf. A000005, A000010 (phi), A008683 (mu), A020488 (fixed points), A051953, A063070.
%Y A351561 Cf. also A055517.
%K A351561 nonn
%O A351561 1,2
%A A351561 _Antti Karttunen_, Feb 21 2022