[seqfan] Re: Is this right? Main diagonal A[n.n] of array A[k, n] = n-th natural number m such that m and m+2 are both divisible by exactly k primes (counted with multiplicity).

[Douglas McNeil]

On Fri, Aug 13, 2010 at 3:07 AM, Jack Brennen <jfb at brennen.net> wrote:
> A[12,12] == 165009150
> A[13,13] == 673932798

I agree, and think I have 14 and 15, so A[k,n=k] begins

[3, 33, 42, 196, 918, 6640, 24750, 246078, 781248, 6565374, 25227774,
165009150, 673932798, 5268548608, 25737162750]

using a crude sieve.  The same dataset gives

[3, 4, 18, 54, 270, 1888, 10528, 59776, 101248, 406782, 6581248,
12164094, 65071998, 652963840, 6548416000, 13858918398]

for A[k,1], although I think this could be found much faster than I'm doing it.


Doug

-- 
Department of Earth Sciences
University of Hong Kong