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 A257751 #13 Sep 03 2015 10:53:33 %S A257751 35,77,143,165,187,209,231,247,273,299,357,391,399,437,493,527,561, %T A257751 589,598,713,715,943,989,1015,1073,1189,1247,1295,1333,1537,1547,1705, %U A257751 1729,1739,1829,1886,1927,1961,2015,2021,2257,2279,2387,2397,2419,2451,2479,2501 %N A257751 Quasi-Carmichael numbers to exactly one base. %C A257751 See A259238 for the corresponding bases. %H A257751 Tim Johannes Ohrtmann, <a href="/A257751/b257751.txt">Table of n, a(n) for n = 1..14688</a> %e A257751 a(1) = 35 because this is the first squarefree composite number n such that exactly one nonzero integer b exists such that for every prime factor p of n, p+b divides n+b (-3): 35=5*7 and 2, 4 both divide 32. %o A257751 (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==1, print1(n, ", "))))) %Y A257751 Cf. A257750 (every number of bases). %Y A257751 Cf. A257752, A257753, A257754, A257755, A257756, A257757, A258842 (2 to 8 bases). %Y A257751 Cf. A257758 (first occurrences). %K A257751 nonn %O A257751 1,1 %A A257751 _Tim Johannes Ohrtmann_, May 07 2015