OFFSET
1,1
COMMENTS
EXAMPLE
a(1) = 4 because A002371(4) Period of decimal expansion of 1/(4th prime) = 6 = 2*3, a semiprime.
a(2) = 6 because A002371(6) = 6 = 2*3.
a(3) = 9 because A002371(9) = 22 = 2*11.
a(4) = 11 because A002371(11) = 15 = 3*5.
a(5) = 14 because A002371(14) = 21 = 3*7.
a(6) = 15 because A002371(15) = 46 = 2*23.
a(7) = 17 because A002371(17) = 58 = 2*29.
MATHEMATICA
semiprimeQ[n_] := Plus @@ Last /@ FactorInteger[n] == 2; PrimePi /@ Select[Prime@ Range@ 254, semiprimeQ@ MultiplicativeOrder[10, # ] &] (* Robert G. Wilson v *)
CROSSREFS
KEYWORD
base,easy,nonn
AUTHOR
Jonathan Vos Post, May 10 2007
EXTENSIONS
Edited, corrected and extended by Robert G. Wilson v, May 22 2007
STATUS
approved