A372056 Smallest prime obtained by appending one or more 3's to n, or -1 if no such prime exists.

13, 23, -1, 43, 53, -1, 73, 83, -1, 103, 113, -1, 1333333333333333, 1433, -1, 163, 173, -1, 193, 20333, -1, 223, 233, -1, 2533333333, 263, -1, 283, 293, -1, 313, 323333, -1, 3433, 353, -1, 373, 383, -1

Offset: 1

Author

Toshitaka Suzuki, Mar 30 2024

Keywords

• base
• sign

Comments

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

Examples

			For n = 13, a(13) = 1333333333333333 is a prime (but 133,1333,13333 etc. are not primes).
		

Links

• Toshitaka Suzuki, Table of n, a(n) for n = 1..409

Crossrefs

See A112394 for another version.

Cf. A030431, A090584, A112386, A113076.

Extensions

Edited by N. J. A. Sloane, Apr 24 2024