[seqfan] Re: A159559

Ray Chandler rayjchandler at sbcglobal.net
Tue Jul 28 21:10:07 CEST 2009

You don't need a special case for a(1)=2 if you define as:

a(n) is non-composite iff n is non-composite. 

Or replace "prime" with "non-composite" in your definition.


> I agree that setting a(1)=2 is natural (taking a(1)=1 gives 
> the positive integers, of course).
> What do you think of this definition:
> a(1)=2 and for n>1, if n is prime (resp. composite) then a(n) 
> is the smallest prime (resp. composite) greater than a(n-1).
> Benoit

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