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 A271221 #35 Apr 25 2024 14:02:05 %S A271221 341,1105,1105,1729,1729,29341,29341,29341,29341,29341,29341,162401, %T A271221 162401,162401,162401,252601,252601,252601,252601,252601,252601, %U A271221 252601,252601,252601,252601,252601,252601,252601,252601,252601,252601,252601,252601,252601,252601,252601,252601,252601,252601 %N A271221 Smallest Fermat pseudoprime k to all bases b = 2, 3, 4, ..., n. %C A271221 a(n) is the smallest composite k such that b^(k-1) == 1 (mod (b-1)k) for every b = 2, 3, 4, ..., n. For more comments, see A083876 and A300629. - _Max Alekseyev_ and _Thomas Ordowski_, Apr 29 2018 %o A271221 (PARI) a(n) = forcomposite(c=1, , my(i=0); for(b=2, n, if(Mod(b, c)^(c-1)==1, i++)); if(i==n-1, return(c))); %Y A271221 Cf. A052155, A083737, A083739, A083876, A300629. %K A271221 nonn %O A271221 2,1 %A A271221 _Felix Fröhlich_, Apr 02 2016 %E A271221 Edited by _Thomas Ordowski_, Apr 29 2018 %E A271221 Corrected a typo within the initial terms by _Jens Ahlström_, Apr 23 2024