OFFSET
1,1
COMMENTS
The numbers starting with 1 are in the set {1, 5, 9} because if another number q = 2k + 1 exists, then k+1, k+3 and k+5 are primes only if k = 2, but q=5 is already in the set.
The numbers starting with 3 are given by A115760.
The numbers starting with 7 are 7, 15, 19, 67, 127, 187, 547, 607, ...
FORMULA
a(n) = 2*A093483(n)+1 (follows from the definition). - Chris Boyd, Mar 16 2014
EXAMPLE
For the set of the first three entries, 5+9 = 2*7, 5+17 = 2*11, 9+17 = 2*13.
MAPLE
A180565 := proc(n) option remember; if n = 1 then 5; else for a from procname(n-1)+1 do wrks := true ; for prev from 1 to n-1 do if not type((procname(prev)+a)/2, prime) then wrks := false; break; end if; end do: if wrks then return a; end if; end do: end if; end proc: # R. J. Mathar, Jan 24 2011
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Michel Lagneau, Jan 21 2011
EXTENSIONS
a(14)-a(17) from Chris Boyd, Mar 16 2014
STATUS
approved