A244270 Numbers n such that n1n2n3n4n5n6n7n8n9n is prime.

17, 53, 181, 313, 343, 377, 829, 859, 943, 1151, 1477, 1493, 1757, 1853, 1909, 2011, 2161, 2267, 2287, 2371, 2521, 2549, 2569, 2773, 2791, 2803, 2849, 2891, 3019, 3157, 3401, 3617, 3811, 3821, 3979, 4273, 4319, 4481, 4483, 4493, 4499, 4607, 5081, 5239, 5299, 5351, 5353, 5399, 5567, 5603, 5669, 5761

Offset

1,1

Comments

a(n) is odd for all n.

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Example

17117217317417517617717817917 is prime. Thus, 17 is a member of this sequence.

Mathematica

Select[Range[1, 6000, 2], PrimeQ[FromDigits[Flatten[IntegerDigits/@Riffle[Range[9], #, {1, -1, 2}]]]]&] (* Harvey P. Dale, Jan 12 2026 *)

Prog

(PARI) for(n=1, 10^4, b=""; for(i=2, 20, if(i==Mod(1, 2), b=concat(b, Str((i-1)/2))); if(i==Mod(0, 2), b=concat(b, Str(n)))); if(ispseudoprime(eval(b)), print1(n, ", ")))

Crossrefs

Sequence in context: A033213 A082078 A107175 * A244271 A224269 A125637

Adjacent sequences: A244267 A244268 A244269 * A244271 A244272 A244273

Keyword

nonn,base,less

Author

Derek Orr, Jun 24 2014

Status

approved