A378122 - OEIS

%I #5 Nov 20 2024 09:50:56

%S 1,1,2,1,2,1,2,2,2,2,2,1,3,1,2,2,3,2,2,2,2,2,3,2,3,2,2,2,3,2,3,2,3,2,

%T 2,2,3,2,3,2,3,2,3,2,3,2,3,2,3,3,3,2,4,2,2,3,4,2,2,1,3,2,3,1,2,2,3,3,

%U 3,3,3,2,3,2,2,3,4,2,3,3,2,2,2,4,3,3

%N a(n) = number of prime divisors of the sum of the first n primes.

%e 2+3+5+7+11 = 28 = 2*2*7, so a(5) = 2.

%t a[n_] := PrimeNu[Total[Prime[Range[n]]]]; Array[a, 500]

%Y Cf. A000040, A071215, A008334, A008335, A378123.

%K nonn

%O 1,3

%A _Clark Kimberling_, Nov 17 2024