OFFSET
1,5
COMMENTS
Observation: Most of the members are prime or 1. The first composite k are a(15)=27, a(21)=9, a(22)=39, a(24)=9, a(27)=51, a(35)=49....
EXAMPLE
a(19) = 7 as 197 and 719 both are prime, a(15) =0.
MAPLE
A083803 := proc(n)
if modp(n, 5) = 3 then
0;
else
for k from 1 do
if isprime(digcat2(k, 2*n-1) ) then
if isprime(digcat2(2*n-1, k)) then
return k;
end if;
end if;
end do:
end if;
end proc: # R. J. Mathar, Aug 23 2014
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Amarnath Murthy and Meenakshi Srikanth (menakan_s(AT)yahoo.com), May 08 2003
EXTENSIONS
More terms from David Wasserman, Nov 30 2004
STATUS
approved