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 A197225 #18 Mar 30 2012 17:23:02 %S A197225 3,11,17,37,41,53,73,79,83,101,107,137,163,173,227,239,257,271,317, %T A197225 347,353,359,449,467,479,563,587,641,643,719,733,751,757,773,797,839, %U A197225 907,1031,1187,1231,1283,1307,1319,1409,1439,1493,1523,1627,1637,1879,1907 %N A197225 Primes p with the period of the decimal fraction 1/p a prime power, A000961. %H A197225 T. D. Noe, <a href="/A197225/b197225.txt">Table of n, a(n) for n = 1..1000</a> %t A197225 myPerfectPowerQ[n_] := Length[FactorInteger[n]] == 1; Select[Prime[Range[500]], Mod[10,#] > 0 && myPerfectPowerQ[Length[RealDigits[1/#, 10][[1,1]]]] &] %Y A197225 Cf. A072859 (period is prime). %Y A197225 Cf. A072982 (period is a power of 2). %Y A197225 Cf. A128948 (period is perfect power). %Y A197225 Cf. A197226 (the periods of this sequence). %Y A197225 Cf. A129727 (period is a semiprime). %K A197225 nonn,base %O A197225 1,1 %A A197225 _T. D. Noe_, Oct 22 2011