OFFSET
1,1
COMMENTS
a(n) is nonzero for n in A006093.
When a(n) is nonzero, a(n) = n*(n+1).
FORMULA
a(A006093(n)) = n*(n+1).
EXAMPLE
2*k/(k-2) is an integer when k=1,2,3,6. The only prime is when k = 6 (2*6/(6-2) = 3 is prime). Thus a(2) = 6.
PROG
(PARI) a(n)=for(k=1, n*(n+1), if(k!=n, s=(k*n)/(k-n); if(floor(s)==s, if(ispseudoprime(s), return(k)))))
n=1; while(n<100, print1(a(n), ", "); n+=1)
CROSSREFS
KEYWORD
nonn
AUTHOR
Derek Orr, May 29 2014
STATUS
approved