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Smallest b > 1 not already in the sequence such that b^(c-1) == 1 (mod c^2), i.e., c is a base-b "Wieferich pseudoprime", where c is the n-th composite number (A002808).
1

%I #5 Jan 19 2019 23:21:54

%S 17,37,65,80,101,145,197,26,257,325,401,244,485,577,182,677,728,177,

%T 901,1025,604,1157,99,1297,1445,170,1601,1765,1937,82,2117,2305,1047,

%U 2501,2024,529,2917,1451,3137,721,3365,3601,3845,3725,4097,168,1945,4625,530

%N Smallest b > 1 not already in the sequence such that b^(c-1) == 1 (mod c^2), i.e., c is a base-b "Wieferich pseudoprime", where c is the n-th composite number (A002808).

%C First differs from A256517 at n = 12.

%C Is this a permutation of the positive integers > 1?

%o (PARI) my(v=vector(1)); forcomposite(c=1, 50, my(b=2); while(Mod(b, c^2)^(c-1)!=1, b++; if(Mod(b, c^2)^(c-1)==1, for(k=1, #v, if(b==v[k], b++)))); v=concat(v, b); print1(v[#v], ", "))

%Y Cf. A002808, A256517, A323602.

%K nonn

%O 1,1

%A _Felix Fröhlich_, Jan 19 2019