A112394 Smallest prime obtained by appending 3's to k, where k runs through the numbers not divisible by 3, or -1 if no such prime exists.

13, 23, 43, 53, 73, 83, 103, 113, 1333333333333333, 1433, 163, 173, 193, 20333, 223, 233, 2533333333, 263, 283, 293, 313, 323333, 3433, 353, 373, 383

Offset

1,1

Comments

Next term is 40 followed by 483 3's, and is too large to display here (see the b-file).

Links

Harvey P. Dale, Table of n, a(n) for n = 1..200

Example

For k = 1, we get the prime 13.
For k = 13, we get the prime 1333333333333333 (the smaller numbers 133,1333,13333 etc. are not primes).
For k = 4070 and 9287, no such prime exists, so we get -1 for the value. Compare A372056. - Toshitaka Suzuki, Mar 30 2024

Mathematica

sp3[n_]:=Module[{idn=IntegerDigits[n], k=1}, While[!PrimeQ[FromDigits[ Join[ idn, PadRight[ {}, k, 3]]]], k++]; FromDigits[Join[idn, PadRight[{}, k, 3]]]]; sp3/@Drop[Range[40], {3, -1, 3}] (* Harvey P. Dale, Jul 11 2017 *)

Crossrefs

See A372056 for another version.

Cf. A112386.

Sequence in context: A119488 A165350 A236418 * A067227 A240113 A256177

Adjacent sequences: A112391 A112392 A112393 * A112395 A112396 A112397

Keyword

nonn,base,changed

Author

Parthasarathy Nambi, Dec 05 2005

Extensions

More terms from Lambert Herrgesell (zero815(AT)googlemail.com), Dec 09 2005

Edited by N. J. A. Sloane, Apr 24 2024. (Escape clause added to definition at the suggestion of Toshitaka Suzuki, Mar 30 2024. See also A372056.)

Status

approved