[seqfan] Re: Biprimes of K

[M. F. Hasler]

A026242 is not increasing.
Does it make sense to apply this sieve in that case?
If one does, the resulting BIP isn't increasing, either; I find
BIP = [2, 3, 4, 5, 8, 15, 20, 35, 50, 37, 40, 46, 109, 124, 134, 92,
183, 198, 223, 159, 272, 282, 205, 214, 356, 371, 406, 445, 480, 495,
312, 321, 569, 579, 367, ...]
(as a sequence), thus
BIP = {2, 3, 4, 5, 8, 15, 20, 35, 37, 40, 46, 50, 92, 109, 124, 134,
159, 183, 198, 205, 214, 223, 272, 282, 312, 321, 356, 367, 371, 406,
445, 480, 495, 569, 579,...}
as a set.

M.

(PARI)
L(n)=min(2000,sqrtint(5*n^2)+n)\2
U(n)=min(2000,sqrtint(5*n^2)+3*n)\2
A026242=vector(1000);for(j=1,999,A026242[L(j)]=j;A026242[U(j)]=j)
BP=A026242[1..999];for(j=3,#BP,BP[j]||next;forstep(j+BP[j],#BP,BP[j]=0));select(f->f,
BP);
Set(BP)


On Tue, Sep 16, 2014 at 10:03 PM, L. Edson Jeffery <lejeffery2 at gmail.com> wrote:
>
> Éric,
>
> Very nice, but we need more terms for A026242. I hope someone will take
> time to extend the b-file.
>
> If you drop the two ones and let K = {2,3,2,4,3,5,...} with offset 1, then
> the sequence of indices for your BIP = 2,3,4,5,8,15,... (non-underlined
> elements of K) starts with 1,2,4,6,10,22 which is interesting as well and
> not in OEIS (unless it happens to be A005194 which is doubtful).
>
> Ed Jeffery