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 A121048 #21 Dec 27 2024 13:28:00
%S A121048 2,3,5,6,9,8,13,12,15,14,21,16,25,20,23,24,33,24,37,28,33,32,45,32,45,
%T A121048 38,45,40,57,38,61,48,53,50,59,48,73,56,63,56,81,54,85,64,69,68,93,64,
%U A121048 91,70,83,76,105,72,95,80,93,86,117,76,121,92,99,96,113,86,133,100,113
%N A121048 a(n) = n + phi(n), where phi is the Euler totient function.
%H A121048 Vincenzo Librandi, <a href="/A121048/b121048.txt">Table of n, a(n) for n = 1..1000</a>
%F A121048 a(n) = n + phi(n) = n + A000010(n).
%F A121048 Sum_{k=1..n} a(k) ~ c * n^2 / 2, where c = 1 + 1/zeta(2) = 1.607927... . - _Amiram Eldar_, Dec 16 2023
%t A121048 Table[n+EulerPhi[n],{n,1,70}]
%o A121048 (Magma) [n + EulerPhi(n): n in [1..70]]; // _Vincenzo Librandi_, Jul 13 2012
%o A121048 (PARI) a(n) = n+eulerphi(n); \\ _Michel Marcus_, Sep 19 2022
%Y A121048 Cf. A000010, A000040, A050530, A051953, A059956, A068080.
%K A121048 easy,nonn
%O A121048 1,1
%A A121048 _Jonathan Vos Post_, Aug 08 2006