

A309383


a(n) is the smallest b > 1 such that when c is equal to any of the first n composites the congruence b^(c1) == 1 (mod c) is satisfied, i.e., smallest b larger than 1 such that any member of the set of smallest n composites is a baseb Fermat pseudoprime.


0



5, 13, 25, 73, 361, 361, 2521, 2521, 5041, 5041, 5041, 5041, 55441, 55441, 277201, 3603601, 10810801, 10810801, 10810801, 21621601, 21621601, 367567201, 367567201, 367567201
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OFFSET

1,1


LINKS



EXAMPLE

For n = 4: The four smallest composites are 4, 6, 8, 9 and for those four values of c the congruence b^(c1) == 1 (mod c) is satisfied with b = 73. Since 73 is the smallest such value of b > 1, a(4) = 73.


PROG

(PARI) composites(n) = my(v=[]); forcomposite(c=1, , v=concat(v, [c]); if(#v >= n, return(v)))
a(n) = my(cp=composites(n)); for(b=2, oo, for(k=1, #cp, if(Mod(b, cp[k])^(cp[k]1)!=1, break, if(k==#cp, return(b)))))


CROSSREFS



KEYWORD

nonn,more


AUTHOR



STATUS

approved



