A271221 - OEIS

%I #35 Apr 25 2024 14:02:05

%S 341,1105,1105,1729,1729,29341,29341,29341,29341,29341,29341,162401,

%T 162401,162401,162401,252601,252601,252601,252601,252601,252601,

%U 252601,252601,252601,252601,252601,252601,252601,252601,252601,252601,252601,252601,252601,252601,252601,252601,252601,252601

%N Smallest Fermat pseudoprime k to all bases b = 2, 3, 4, ..., n.

%C 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 (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 Cf. A052155, A083737, A083739, A083876, A300629.

%K nonn

%O 2,1

%A _Felix Fröhlich_, Apr 02 2016

%E Edited by _Thomas Ordowski_, Apr 29 2018

%E Corrected a typo within the initial terms by _Jens Ahlström_, Apr 23 2024