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 A038344 #21 Sep 08 2022 08:44:53
%S A038344 1,8,9,32,36,50,100,225,242,484,512,578,729,800,900,1089,1156,1250,
%T A038344 1936,2025,2048,2304,2312,2601,2916,3025,3872,4418,6400,7225,7744,
%U A038344 8192,8464,8836,9216,10000,12800,14400,20000,20736,21609,26896,27556,31684,32768,33856,34322
%N A038344 Numbers k such that phi(k) + sigma(k) is a prime.
%C A038344 Indices k such that A065387(k) is a prime number. - _R. J. Mathar_, Aug 26 2009
%C A038344 All terms are squares or twice squares (A028982). - _Donovan Johnson_, Sep 27 2013
%H A038344 Donovan Johnson, <a href="/A038344/b038344.txt">Table of n, a(n) for n = 1..1000</a>
%F A038344 {k: A000203(k) + A000010(k) in A000040}. - _R. J. Mathar_, Aug 26 2009
%e A038344 a(2) = 8 because phi(8) + sigma(8) = 19.
%t A038344 Select[Range[0, 40000], PrimeQ[DivisorSigma[1, #] + EulerPhi[#]] &] (* _Vincenzo Librandi_, Jul 22 2016 *)
%o A038344 (PARI) isok(n) = isprime(eulerphi(n) + sigma(n)); \\ _Michel Marcus_, Sep 27 2013
%o A038344 (PARI) v=vector(1000); c=0; for(j=1, 12105, m=j^2; if(isprime(eulerphi(m)+sigma(m)), c++; v[c]=m)); for(j=1, 8559, m=2*j^2; if(isprime(eulerphi(m)+sigma(m)), c++; v[c]=m)); v=vecsort(v); for(n=1, 1000, write("b038344.txt", n " " v[n])) \\ _Donovan Johnson_, Sep 27 2013
%o A038344 (Magma) [n: n in [1..40000] | IsPrime(EulerPhi(n)+DivisorSigma(1,n))]; // _Vincenzo Librandi_, Jul 22 2016
%Y A038344 Cf. A000010, A000027, A000040, A000203, A028982.
%K A038344 nonn
%O A038344 1,2
%A A038344 _Felice Russo_
%E A038344 More terms from _Olivier Gérard_