A378122 a(n) = number of prime divisors of the sum of the first n primes.

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, 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, 3, 3, 3, 2, 3, 2, 2, 3, 4, 2, 3, 3, 2, 2, 2, 4, 3, 3

Offset

1,3

Links

Table of n, a(n) for n=1..86.

Example

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

Mathematica

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

Crossrefs

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

Sequence in context: A260341 A109969 A085035 * A198333 A191591 A083023

Adjacent sequences: A378119 A378120 A378121 * A378123 A378124 A378125

Keyword

nonn

Author

Clark Kimberling, Nov 17 2024

Status

approved