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Number of distinct prime divisors of A000129(n) (Pell numbers).
5

%I #16 Oct 21 2023 23:23:00

%S 0,1,1,2,1,3,1,3,2,3,1,5,1,3,3,4,2,5,2,6,3,4,2,7,3,4,4,6,1,7,3,5,3,5,

%T 3,9,3,4,4,9,1,7,2,8,6,5,2,10,3,6,5,7,1,8,5,8,5,3,1,13,3,6,6,8,6,8,2,

%U 9,4,8,3,13,2,7,8,9,5,10,4,12,7,5,2,14,7

%N Number of distinct prime divisors of A000129(n) (Pell numbers).

%H Amiram Eldar, <a href="/A364818/b364818.txt">Table of n, a(n) for n = 1..630</a>

%F a(n) = omega(Pell(n)) = A001221(A000129(n)).

%e a(8)=3 because Pell(8)=408 has prime factors {2, 2, 2, 3, 17}.

%t PrimeNu[LinearRecurrence[{2, 1}, {1, 2}, 85]] (* _Amiram Eldar_, Oct 21 2023 *)

%Y Cf. A000129, A001221, A272040, A363829, A363831, A363833.

%K nonn

%O 1,4

%A _Tyler Busby_, Oct 21 2023