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 A167797 #9 Jan 04 2025 00:33:54 %S A167797 7,17,19,23,29,47,49,59,61,97,109,113,131,149,167,179,181,193,223,229, %T A167797 233,257,263,269,289,313,337,343,361,367,379,383,389,419,433,461,487, %U A167797 491,499,503,509,529,541,571,577,593,619,647,659,701,709,727,743,811 %N A167797 Numbers with primitive root 10. %C A167797 Numbers n such that the decimal expansion of 1/n has period phi(n). For example, 1/49 has period 42. %H A167797 Vincenzo Librandi, <a href="/A167797/b167797.txt">Table of n, a(n) for n = 1..1000</a> %t A167797 pr=10; Select[Range[2,2000], MultiplicativeOrder[pr,# ] == EulerPhi[ # ] &] %o A167797 (PARI) is(n)=if(gcd(n, 10)>1, return(0)); my(p=eulerphi(n)); znorder(Mod(10, n), p)==p \\ _Charles R Greathouse IV_, Jan 04 2025 %Y A167797 Cf. A001913 (primes with primitive root 10) %K A167797 nonn %O A167797 1,1 %A A167797 _T. D. Noe_, Nov 12 2009