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 A258842 #14 Sep 26 2015 12:36:12 %S A258842 182293,6536953,13116283,23337661,55898473,56624329,66112261,66355291, %T A258842 66846751,67239919,75289033,76222261,93331321,97594157,110397013, %U A258842 115175383,146385797,147111617,157333573,158029141,159289241,163825601,181950817,187826449,207820831 %N A258842 Quasi-Carmichael numbers to exactly eight bases. %C A258842 All known terms have only two prime factors whereby the second prime factor is only slightly larger than the first. %C A258842 a(3384) > 10^12. - _Hiroaki Yamanouchi_, Sep 26 2015 %H A258842 Hiroaki Yamanouchi, <a href="/A258842/b258842.txt">Table of n, a(n) for n = 1..3383</a> %e A258842 a(1) = 182293 because this is the first squarefree composite number n such that exactly eight integers except 0 exist such that for every prime factor p of n applies that p+b divides n+b (-419, -418, -413, -412, -405, -403, -373, -349): 182293=421*433 and 2, 14 both divide 181874 and 3, 15 both divide 181875 and 8, 20 both divide 181880 and 9, 21 both divide 181881 and 16, 28 both divide 181888 and 18, 30 both divide 181890 and 48, 60 both divide 181920 and 72, 84 both divide 181944. %o A258842 (PARI) for(n=2, 1000000, if(!isprime(n), if(issquarefree(n), f=factor(n); k=0; for(b=-(f[1, 1]-1), n, c=0; for(i=1, #f[, 1], if((n+b)%(f[i, 1]+b)>0, c++)); if(c==0, if(!b==0, k++))); if(k==8, print1(n, ", "))))) %Y A258842 Cf. A257750 (every number of bases). %Y A258842 Cf. A257751, A257752, A257753, A257754, A257755, A257756, A257757 (1 to 7 bases). %Y A258842 Cf. A257758 (first occurrences). %K A258842 nonn %O A258842 1,1 %A A258842 _Tim Johannes Ohrtmann_, Jun 12 2015 %E A258842 a(4)-a(25) from _Hiroaki Yamanouchi_, Sep 26 2015