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%I #8 Apr 21 2018 18:29:09
%S 4,6,7,11,87,98,215,802,4202,18699,96879
%N Indices of primes in tribonacci sequence A000073.
%C T = A000073 is defined by T(n+1) = T(n) + T(n-1) + T(n-2), T(2) = 1, T(1) = T(0) = 0.
%C The largest terms correspond to unproven probable primes T(a(n)).
%F a(n) = A092835(n) + 1 = index of A092836(n) in A000073.
%t -1 + Position[LinearRecurrence[{1, 1, 1}, {0, 0, 1}, 10^4], _?PrimeQ][[All, 1]] (* _Michael De Vlieger_, Apr 21 2018 *)
%o (PARI) a(n,N=4,S=vector(N,i,i>N-2))={for(i=N,oo,ispseudoprime(S[i%N+1]=2*S[(i-1)%N+1]-S[i%N+1])&&!n--&&return(i))}
%Y Cf. A000073 (= T), A092836 (= T(a(n))), A092835 (= a(n) - 1).
%Y Cf. A001605 (indices of primes in Fibonacci numbers A000045).
%K nonn,hard,more
%O 1,1
%A _M. F. Hasler_, Apr 18 2018
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