[seqfan] A combinatorial problem

Vladimir Shevelev shevelev at bgu.ac.il
Mon Aug 2 11:11:08 CEST 2010


Dear SeqFans,

I have submitted the following sequence:

%I A179926
%S A179926 0,1,1,1,1,2,1,1,1,2,1,2,1,2,2,1,1,2,1,2,2,2,1,4,1,2,1,2,1,12,1,1,2,2,2,
%T A179926 2,1,2,2,4,1,12,1,2,2,2,1
%N A179926 a(n) is the number of arrangements of all divisors of n of the form d_1=n, d_2, d_3,...,d_tau(n) such that d_(i+1)/d_i is prime or 1/prime 
%C A179926 In view of formulas given below, there are many common first terms with A001221. 
%F A179926 a(p^k)=1, a(p*q)=a(p^2*q)=a(p^2*q^2)=2, a(p^3*q)=4, a(pqr)=12 (here p,q,r are distinct primes, k>=1). 
%Y A179926 A000005 A001221 
%K A179926 nonn
%O A179926 1,1

More terms? More formulas? Corrections?

Regards,
Vladimir

 Shevelev Vladimir‎



More information about the SeqFan mailing list