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 A147969 #8 May 13 2013 01:54:10 %S A147969 2,7,23,23,71,71,311,311,311,311,479,479,1559,1559,1559,1559,5711, %T A147969 5711,10559,10559,10559,10559,18191,18191,18191,18191,18191,18191, %U A147969 31391,31391,366791,366791,366791,366791,366791,366791,366791,366791,366791 %N A147969 Smallest prime p modulo which numbers 1,2,...,n are quadratic residues. %C A147969 The same primes without repetitions are listed in A147970. %H A147969 Charles R Greathouse IV, <a href="/A147969/b147969.txt">Table of n, a(n) for n = 1..100</a> %o A147969 (PARI) a(n)=forprime(p=2,default(primelimit),forprime(i=2,n, if(kronecker(i,p)<1,next(2)));return(p)) \\ _Charles R Greathouse IV_, Apr 06 2012 %Y A147969 Cf. A000229, A002223, A002224, A045535, A053760, A133435, A147970, A147971. %K A147969 nonn %O A147969 1,1 %A A147969 _Max Alekseyev_, Nov 18 2008