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 A343148 #13 Apr 09 2021 09:50:53 %S A343148 2,6,10,15,21,26,28,30,35,38,39,40,42,44,45,46,51,55,60,63,68,69,70, %T A343148 78,84,93,95,96,102,105,106,116,123,124,126,130,135,136,138,143,146, %U A343148 150,153,155,166,174,176,178,201,203,205,218,219,221,222,231,232,234,236,240,244,245,246,248,249 %N A343148 Numbers k such that A083266(k) is prime. %C A343148 Includes 2*p for p in A157468. %H A343148 Robert Israel, <a href="/A343148/b343148.txt">Table of n, a(n) for n = 1..10000</a> %e A343148 a(3) = 10 is a term because A083266(10) = 37 is prime. %p A343148 f:= n -> numtheory:-sigma(n) + n*numtheory:-phi(n)/2 - 1: %p A343148 select(t -> isprime(f(t)), [$2..1000]); %t A343148 Select[Range[250], PrimeQ[DivisorSigma[1, #] + # EulerPhi[#]/2 - 1] &] (* _Michael De Vlieger_, Apr 07 2021 *) %Y A343148 Cf. A083266, A157468, A343151. %K A343148 nonn %O A343148 1,1 %A A343148 _J. M. Bergot_ and _Robert Israel_, Apr 06 2021