OFFSET
1,1
COMMENTS
For any fixed integer m>=1 define u(1)=1 and u(n)=abs(u(n-1)-gcd(u(n-1),m*n-1)). Then (b_m(k))_{k>=1} is the sequence of integers such that u(b_m(k))=0 and we conjecture that for k large enough m*b_m(k)+m-1 is a prime number. Here for m=9 it appears a(n) is prime for n>=2.
See A261309 for the sequence u relevant here (m=9). - M. F. Hasler, Aug 14 2015
LINKS
B. Cloitre, 10 conjectures in additive number theory, preprint arxiv:2011.4274 (2011).
M. F. Hasler, Rowland-CloƮtre type prime generating sequences, OEIS Wiki, August 2015.
FORMULA
We conjecture that a(n) is asymptotic to c*10^n with c>0.
See the wiki link for a sketch of a proof of this conjecture. We find c=2.59490352... - M. F. Hasler, Aug 22 2015
PROG
(PARI) a=1; m=9; for(n=2, 1e8, a=abs(a-gcd(a, m*n-1)); if(a==0, print1(m*n+m-1, ", ")))
(PARI) m=9; a=0; k=2; for(n=1, 20, while(1<#(f=factor(N=m*(k+a)+m-1)[, 1]) && a, k+=1+D=vecmin(apply(p->a%p, f)); a-=D+gcd(a-D, N)); k+=a+1; print1(a=N, ", ")) \\ M. F. Hasler, Aug 22 2015
CROSSREFS
KEYWORD
nonn
AUTHOR
Benoit Cloitre, Feb 16 2011
EXTENSIONS
Edited by M. F. Hasler, Aug 14 2015
STATUS
approved