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 A219030 #21 Jan 12 2024 01:15:08 %S A219030 49,289,343,529,961,1681,1849,2209,2401,4913,5041,5329,6241,7921,9409, %T A219030 10609,11881,12167,12769,16129,16807,18769,22801,24649,27889,29791, %U A219030 36481,37249,39601,49729,52441,54289,57121,58081,63001,66049,68921,69169,73441 %N A219030 Powers of odd primes (exponent > 1) for which 2 is not a primitive root. %H A219030 Amiram Eldar, <a href="/A219030/b219030.txt">Table of n, a(n) for n = 1..10000</a> %o A219030 (PARI) for(n=3,100000,if(n%2==1&&isprime(n)==0&&znorder(Mod(2,n))!=eulerphi(n)&&matsize(factor(n))[1]==1,print1(n","))) %o A219030 (PARI) list(lim)=my(v=List(),L=log(lim+.5));forprime(p=3,sqrtint(lim\1), for(e=2,L\log(p), if(znorder(Mod(2,p^e))<p^(e-1)*(p-1), listput(v,p^e)))); vecsort(Vec(v)) \\ _Charles R Greathouse IV_, Nov 12 2012 %Y A219030 Cf. A167791, A216848, A108989. %K A219030 nonn %O A219030 1,1 %A A219030 _V. Raman_, Nov 10 2012