24 Sep
2003
24 Sep
'03
10:11 a.m.
From; http://www.research.att.com/projects/OEIS?Anum=A000203 we have; sigma(n) = n*P(n) - sum{i=1,n-1,a(i)*P(n-i)} , where P(n)=A000041(n) Examining sigma(n)-sigma(n-1), we find a few nice algebraic drop-outs, and end with; sigma(n)=n[P(n)-P(n-1)] + sigma(n-2) - sum{i=1,n-3,P(n-i-1)*[sigma(i+1)-sigma(i)]} which is just as useless as before, however the use of the differences is interesting... Jon Perry perry@globalnet.co.uk http://www.users.globalnet.co.uk/~perry/maths/ http://www.users.globalnet.co.uk/~perry/DIVMenu/ BrainBench MVP for HTML and JavaScript http://www.brainbench.com