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 A234387 a(n) = n-th smallest prime congruent to 1 modulo prime(n). 1

%I

%S 3,13,41,113,331,443,613,1103,1013,1741,2543,3257,3691,4129,4889,6997,

%T 6491,8053,8443,12071,11681,12799,15439,18869,20759,21211,20807,27179,

%U 33791,28703,37339,39301,37813,53377,51853,54059,62801,60637,74149,72661,77687,62989,81749,79903,79589,109849,102547

%N a(n) = n-th smallest prime congruent to 1 modulo prime(n).

%H Zak Seidov and Charles R Greathouse IV, <a href="/A234387/b234387.txt">Table of n, a(n) for n = 1..10000</a> (first 1000 terms from Seidov)

%e a(3) = 41 because prime(3) = 5 and primes == 1 mod 5 are 11, 31, 41;

%e a(4) = 113 because prime(4) = 7 and primes == 1 mod 7 are 29, 43, 71, 113.

%t Reap[Sow;Do[c=0;q=Prime[n];p=1;While[c<n,p=p+2q;If[PrimeQ[p],c++]];Sow[p],{n,2,100}]][[2,1]]

%o (PARI) a(n)=if(n<2,return(3)); my(p=prime(n),q=2*p+1); while(n, if(isprime(q), n--); q+= 2*p); q-2*p \\ _Charles R Greathouse IV_, Dec 26 2013

%Y Cf. A035095, A234372.

%K nonn

%O 1,1

%A _Zak Seidov_, Dec 25 2013

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Last modified March 31 21:40 EDT 2023. Contains 361673 sequences. (Running on oeis4.)