A303264 - OEIS

%I #17 Jul 21 2021 22:49:44

%S 5,9,13,14,38,58,403,2709,8419,14098,31563,50698,53194,155184

%N Indices of primes in tetranacci sequence A000078.

%C T = A000078 is defined by T(n) = Sum_{k=1..4} T(n-k), T(3) = 1, T(n) = 0 for n < 3.

%C The largest terms correspond to unproven probable primes T(a(n)).

%F a(n) = A104534(n) + 2.

%o (PARI) a(n,N=5,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. A000045, A000073, A000078, A001591, A001592, A122189 (or A066178), ... (Fibonacci, tribonacci, tetranacci numbers).

%Y Cf. A005478, A092836, A104535, A105757, A105759, A105761, ... (primes in Fibonacci numbers and above generalizations).

%Y Cf. A001605, A303263, A303264, A248757, A249635, ... (indices of primes in A000045, A000073, A000078, ...).

%Y Cf. A247027: Indices of primes in the tetranacci sequence A001631 (starting 0, 0, 1, 0...), A104534 (a variant: a(n) - 2), A105756 (= A248757 - 3), A105758 (= A249635 - 4).

%K nonn,hard,more

%O 1,1

%A _M. F. Hasler_, Apr 18 2018