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Least number for which Solovay-Strassen primality test on bases < prime(n) fails.
(Formerly M5443)
3

%I M5443 #17 Jun 04 2022 08:00:25

%S 9,561,1729,1729,399001,399001,1857241,1857241,6189121,14469841,

%T 14469841,14469841

%N Least number for which Solovay-Strassen primality test on bases < prime(n) fails.

%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

%H Wikipedia, <a href="https://en.wikipedia.org/wiki/Solovay%E2%80%93Strassen_primality_test">Solovay-Strassen primality test</a>

%o (PARI) a(n) = my(b, p=factorback(primes(n-1))); forcomposite(k=9, oo, if(gcd(k, p)==1, b=2; while(Mod(b, k)^(k\2) == kronecker(b, k), b++); if(b>=prime(n), return(k)))); \\ _Jinyuan Wang_, Jun 04 2022

%Y Cf. A083876, A271221, A329726.

%K nonn,more

%O 1,1

%A _N. J. A. Sloane_, Eric Bach (bach(AT)cs.wisc.edu)

%E Offset changed to 1 and a(1) corrected by _Jinyuan Wang_, Jun 04 2022