This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A122183 #9 Jul 11 2015 11:27:58 %S A122183 4,6,9,11,14,15,17,19,20,26,27,34,39,41,43,56,59,61,62,64,76,83,85,86, %T A122183 96,101,102,109,111,112,119,124,138,140,144,147,149,150,154,161,166, %U A122183 168,170,171,175,192,198,203,216,219,222,224,225,235,236,239,240,246,251 %N A122183 Primes p_i by index i for which the period length of 1/p_i is a semiprime. %C A122183 Semiprime analog of A072859 based on A002371. %C A122183 Numbers n such that A002371(n) is an element of A001358. %e A122183 a(1) = 4 because A002371(4) Period of decimal expansion of 1/(4th prime) = 6 = 2*3, a semiprime. %e A122183 a(2) = 6 because A002371(6) = 6 = 2*3. %e A122183 a(3) = 9 because A002371(9) = 22 = 2*11. %e A122183 a(4) = 11 because A002371(11) = 15 = 3*5. %e A122183 a(5) = 14 because A002371(14) = 21 = 3*7. %e A122183 a(6) = 15 because A002371(15) = 46 = 2*23. %e A122183 a(7) = 17 because A002371(17) = 58 = 2*29. %t A122183 semiprimeQ[n_] := Plus @@ Last /@ FactorInteger[n] == 2; PrimePi /@ Select[Prime@ Range@ 254, semiprimeQ@ MultiplicativeOrder[10, # ] &] (* _Robert G. Wilson v_ *) %Y A122183 Cf. A000040, A001358, A002371, A072859, A128948. %K A122183 base,easy,nonn %O A122183 1,1 %A A122183 _Jonathan Vos Post_, May 10 2007 %E A122183 Edited, corrected and extended by _Robert G. Wilson v_, May 22 2007