A109369 Numbers n such that the string 33n is the decimal expansion of a prime number.

1, 7, 13, 19, 23, 29, 31, 43, 47, 59, 61, 71, 73, 89, 91, 107, 113, 119, 149, 151, 161, 179, 181, 191, 199, 203, 211, 223, 247, 287, 289, 301, 311, 317, 329, 331, 343, 347, 349, 353, 359, 377, 391, 403, 409, 413, 427, 457, 461, 469, 479, 487, 493, 503, 521

Offset

1,2

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..2000

Example

1 is in the sequence because 331 is prime.
59 is in the sequence because 3359 is prime.
107 is in the sequence because 33107 is prime.

Maple

a:=proc(n) if isprime(33*10^nops(convert(n, base, 10))+n)=true then n else fi end: seq(a(n), n=0..600); # Emeric Deutsch, Sep 02 2005

Mathematica

Select[Range[600], PrimeQ[33*10^IntegerLength[#]+#]&] (* Harvey P. Dale, Jul 29 2014 *)

Prog

(Magma) [ n: n in [1..600] | IsPrime(Seqint(Intseq(n) cat [3, 3])) ];

Crossrefs

Sequence in context: A007921 A092409 A124095 * A336373 A320629 A371166

Adjacent sequences: A109366 A109367 A109368 * A109370 A109371 A109372

Keyword

nonn,base

Author

Parthasarathy Nambi, Aug 24 2005

Extensions

More terms from Emeric Deutsch, Sep 02 2005

Status

approved