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

1,1

Comments

Includes 2*p for p in A157468.

Links

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

Example

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

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 *)

Crossrefs

Cf. A083266, A157468, A343151.

Sequence in context: A288631 A276211 A190091 * A331250 A186783 A133931

Adjacent sequences: A343145 A343146 A343147 * A343149 A343150 A343151

Keyword

nonn

Author

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

Status

approved