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
KEYWORD
nonn
AUTHOR
J. M. Bergot and Robert Israel, Apr 06 2021
STATUS
approved