OFFSET
1,1
COMMENTS
Conjecture: 1 and 5 are the only two odd nonmembers.
EXAMPLE
2,29,293,29327,...etc. are primes.
MATHEMATICA
p = Prime[ Range[ 1000]]; np = Complement[ Range[ 1000], p]; a[n_] := a[n] = Block[{k = 1, q = Flatten[ IntegerDigits[ # ] & /@ Table[ a[i], {i, n - 1}]]}, If[ OddQ[n], While[ !PrimeQ[ FromDigits[ Join[q, IntegerDigits[ p[[k]] ]]]], k++ ]; q = p[[k]]; p = Delete[p, k]; q, While[ !PrimeQ[ FromDigits[ Join[q, IntegerDigits[ np[[k]] ]]]], k++ ]; q = np[[k]]; np = Delete[np, k]; q]]; Table[ a[n], {n, 56}] (* Robert G. Wilson v, Apr 23 2004 *)
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Amarnath Murthy, Oct 16 2003
EXTENSIONS
More terms from Ray Chandler, Oct 18 2003
STATUS
approved