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A109887 Numbers n such that 3^n + phi(n) is prime. 0
3, 4, 10, 20, 44, 60, 583, 677, 947, 1182, 12048, 16018, 74316 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

All terms correspond to certified primes (Primo 2.2.0 beta). No more terms through 10000.

a(14) > 10^5. [From Donovan Johnson, Feb 06 2010]

LINKS

Table of n, a(n) for n=1..13.

MATHEMATICA

Do[If[PrimeQ[3^n + EulerPhi[n]], Print[n]], {n, 1, 10000}]

CROSSREFS

Sequence in context: A036649 A255539 A321197 * A200981 A266729 A103038

Adjacent sequences:  A109884 A109885 A109886 * A109888 A109889 A109890

KEYWORD

hard,nonn

AUTHOR

Ryan Propper, Aug 31 2005

EXTENSIONS

a(11)-a(13) from Donovan Johnson, Feb 06 2010

STATUS

approved

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Last modified February 23 12:03 EST 2019. Contains 320431 sequences. (Running on oeis4.)