# A80435

Ralf Stephan ralf at ark.in-berlin.de
Mon Apr 14 09:22:20 CEST 2003

```judmccr wrote
> A80435 seems ambiguous or incorrect.  I wrote to the author asking for a
> clarification 4 days ago, but I haven't gotten a reply.

%S A080435 1,2,3,5,8,15,17
%N A080435 Distinct numbers such that if a(i) + a(j) is a prime p then p is so obtained uniquely (no other pair of members has sum p).

I'd add 'smallest', then I get

? v=vector(1000):v[1]=1:vv=vector(1000):vv[1]=1:n=1:while(n<100,n=n+1:for(m=1,10^9,f=0:if(!vv[m],v[n]=m:w=vector(1000):for(k=2,n,for(l=1,k-1,s=v[k]+v[l]:if(isprime(s),if(w[s],f=1:break,w[s]=1))):if(f,break)):if(!f,print1(m","):vv[m]=1:break))))

1,2,3,5,7,8,13,14,19,20,23,25,27,31,37,43,47,49,50,55,57,61,67,73,75,79,85,91,97,98,103,107,109,111,115,121,127,131,133,135,139,140,145,151,157,163,169,175,181,185,187,193,199,200,205,211,212,217,223,229,235,239,241,245,247,253,259,265,271,273,277,283,289,
***   user interrupt after 4mn, 28,170 ms.

> First, why isn't 7 in the sequence?  Is it because it doesn't yield any new
> primes when summed with the previous terms?  If that is correct, then why
> isn't 14 in the sequence, since it yields 14+3=17?

good questions...

ralf

```