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A343148
Numbers k such that A083266(k) is prime.
2
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
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