A271221 Smallest Fermat pseudoprime k to all bases b = 2, 3, 4, ..., n.

341, 1105, 1105, 1729, 1729, 29341, 29341, 29341, 29341, 29341, 29341, 162401, 162401, 162401, 162401, 252601, 252601, 252601, 252601, 252601, 252601, 252601, 252601, 252601, 252601, 252601, 252601, 252601, 252601, 252601, 252601, 252601, 252601, 252601, 252601, 252601, 252601, 252601, 252601

Offset: 2

Author

Felix Fröhlich, Apr 02 2016

Keywords

• nonn

Comments

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

Crossrefs

Cf. A052155, A083737, A083739, A083876, A300629.

Programs

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)));

Extensions

Edited by Thomas Ordowski, Apr 29 2018

Corrected a typo within the initial terms by Jens Ahlström, Apr 23 2024