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A110196
Numbers n such that k=2n is the least k such that phi(n+k)=2*phi(k).
1
1, 13, 23, 97, 113, 131, 199, 227, 491, 859, 929
OFFSET
1,2
COMMENTS
No other n < 10^6. Note that all n>1 are primes.
MATHEMATICA
Do[k=1; While[EulerPhi[n+k] != 2*EulerPhi[k], k++ ]; If[k==2n, Print[n]], {n, 5000}]
CROSSREFS
Cf. A050473 (least k such that phi(n+k)=2*phi(k)).
Sequence in context: A155093 A147443 A131447 * A039448 A299361 A089768
KEYWORD
nonn
AUTHOR
T. D. Noe, Jul 15 2005
STATUS
approved