A343148 Numbers k such that A083266(k) is prime.

2, 6, 10, 15, 21, 26, 28, 30, 35, 38, 39, 40, 42, 44, 45, 46, 51, 55, 60, 63, 68, 69, 70, 78, 84, 93, 95, 96, 102, 105, 106, 116, 123, 124, 126, 130, 135, 136, 138, 143, 146, 150, 153, 155, 166, 174, 176, 178, 201, 203, 205, 218, 219, 221, 222, 231, 232, 234, 236, 240, 244, 245, 246, 248, 249

Offset: 1

Author

J. M. Bergot and Robert Israel, Apr 06 2021

Keywords

• nonn

Comments

Includes 2*p for p in A157468.

Examples

			a(3) = 10 is a term because A083266(10) = 37 is prime.
		

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A083266, A157468, A343151.

Programs

Maple

f:= n -> numtheory:-sigma(n) + n*numtheory:-phi(n)/2 - 1:
select(t -> isprime(f(t)), [$2..1000]);

Mathematica

Select[Range[250], PrimeQ[DivisorSigma[1, #] + # EulerPhi[#]/2 - 1] &] (* Michael De Vlieger, Apr 07 2021 *)