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Smallest pseudoprime (>prime(n)) to base prime(n).
2

%I #47 Mar 09 2015 06:56:46

%S 341,91,124,25,15,21,45,45,33,35,49,45,105,77,65,65,87,91,85,105,111,

%T 91,105,99,105,175,133,133,117,133,153,143,148,161,175,175,186,186,

%U 231,205,185,195,217,276,231,225,217,231,285,285,259,255,363,289,301,341,286,341,322,329

%N Smallest pseudoprime (>prime(n)) to base prime(n).

%C Subsequence of A007535, see formula.

%H Eric Chen, <a href="/A250199/b250199.txt">Table of n, a(n) for n = 1..4096</a>

%F a(n) = A007535(A000040(n)).

%e a(7) = 45 because the 7th prime is 17, and the smallest pseudoprime (> 17) to base 17 is 45.

%t f[n_] := Block[{b = Prime[n], k = Prime[n] + 1}, While[PrimeQ[k] || PowerMod[b, k - 1, k] != 1, k++]; k]; Array[f, 60]

%o a(n) = for(k=prime(n)+1,2^24,if(Mod(prime(n),k)^(k-1)==Mod(1,k) && !isprime(k),return(k)))

%Y Cf. A007535, A090086, A108162, A098650.

%K nonn

%O 1,1

%A _Eric Chen_, Feb 21 2015