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A072344 a(n) = the least natural number k such that k*phi(n) + 1 is prime. 0
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 1, 1, 1, 2, 1, 1, 1, 2, 2, 1, 1, 1, 1, 2, 1, 1, 2, 1, 3, 1, 1, 1, 3, 1, 1, 1, 1, 2, 3, 1, 1, 1, 1, 2, 3, 3, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 3, 2, 2, 1, 3, 2, 3, 1, 3, 1, 1, 1, 1, 1, 3, 1, 3, 2, 1, 1, 3, 3, 1, 2, 1, 1, 3, 1, 2, 1, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 2, 2 (list; graph; refs; listen; history; internal format)
OFFSET

1,15

EXAMPLE

phi(35) = 24 and the least natural number k such that 24 k + 1 is prime is k = 3; so a(35) = 3.

MATHEMATICA

f[n_] := Module[{i}, i = 0; While[ ! PrimeQ[i*EulerPhi[n] + 1], i++ ]; i]; Table[f[i], {i, 1, 150}]

CROSSREFS

Sequence in context: A079674 A113193 A117898 * A140500 A156054 A030616

Adjacent sequences:  A072341 A072342 A072343 * A072345 A072346 A072347

KEYWORD

nonn

AUTHOR

Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Jul 16 2002

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Last modified February 14 01:34 EST 2012. Contains 205567 sequences.