A140610 Running prime totals of prime factors (without multiplicity) of consecutive composite N.

2, 7, 19, 41, 43, 83, 103, 127, 233, 569, 673, 683, 1069, 1217, 1571, 2609, 2713, 2957, 3371, 3671, 3847, 3919, 4957, 4973, 6229, 7193, 7253, 7639, 8161, 8527, 9439, 9949, 10159, 12959, 13687, 13763, 13831, 13967, 15497, 16741, 17681, 17807, 20047

Offset

1,1

Links

Table of n, a(n) for n=1..43.

Formula

Compute prime factors (without multiplicity) of consecutive composite N. Maintain a running sum of these prime factors. Whenever the running total at N is prime, add to the sequence.

Example

a(2)=7 because when N=6 the sum of composite prime factors is 7 and this total is prime (nonprime totals are not in this sequence). The prime factor (without multiplicity) of the first composite 4 is 2; the second composite is 6 with prime factors 3 and 2, so 2+2+3=7, the prime sum of prime factors at N=6.

Crossrefs

Cf. A140611.

Sequence in context: A334520 A308269 A038562 * A152461 A215208 A100119

Adjacent sequences: A140607 A140608 A140609 * A140611 A140612 A140613

Keyword

easy,nonn

Author

Enoch Haga, May 19 2008

Status

approved