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A101299 Numbers n such that Sum(phi(x),x=0..n)-1 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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..62.

EXAMPLE

3 = phi(1)+phi(2)+phi(3)-1 ==> 3

5 = phi(1)+phi(2)+phi(3)+phi(4)-1 ==> 4

11 = phi(1)+phi(2)+phi(3)+phi(4)+phi(5)+phi(6)-1 ==>6

17 = phi(1)+phi(2)+phi(3)+phi(4)+phi(6)+phi(7)-1 ==> 7

MAPLE

with(numtheory): a:=proc(n) if isprime(sum(phi(x), x=1..n)-1)=true then n else fi end: seq(a(n), n=1..300); (Deutsch)

CROSSREFS

Sequence in context: A191926 A065135 A229792 * A143837 A206903 A157611

Adjacent sequences:  A101296 A101297 A101298 * A101300 A101301 A101302

KEYWORD

nonn,easy

AUTHOR

Jorge Coveiro (jorgecoveiro(AT)yahoo.com), Dec 22 2004

EXTENSIONS

More terms from Emeric Deutsch, Jul 20 2005

STATUS

approved

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Last modified January 17 16:11 EST 2019. Contains 319235 sequences. (Running on oeis4.)