

A101299


Numbers n such that 1 + Sum_{x=1..n} phi(x) is a prime number.


0



3, 4, 6, 7, 10, 11, 15, 16, 18, 20, 21, 22, 24, 25, 26, 27, 28, 29, 30, 31, 34, 35, 37, 38, 42, 50, 52, 53, 64, 65, 66, 70, 77, 79, 83, 91, 105, 113, 116, 126, 127, 128, 130, 132, 133, 135, 138, 141, 144, 150, 152, 157, 159, 161, 164, 168, 189, 198, 224, 225, 231, 241
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OFFSET

1,1


LINKS



EXAMPLE

3 = phi(1)+phi(2)+phi(3)1 ==> 3, a prime, so 3 is a term.
5 = phi(1)+phi(2)+phi(3)+phi(4)1 ==> 4, not a prime, so 5 is not a term.


MAPLE

with(numtheory): select(n> isprime(add(phi(x), x=1..n)1), [$1..300])[]; # Emeric Deutsch, Jul 20 2005


PROG

(PARI) isok(n) = isprime(sum(k=1, n, eulerphi(k))1); \\ Michel Marcus, Aug 21 2019


CROSSREFS



KEYWORD

nonn,easy


AUTHOR



EXTENSIONS



STATUS

approved



