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
Examples
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.
Links
- Vincenzo Librandi, Table of n, a(n) for n = 1..2000
Programs
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Magma
[ n: n in [1..600] | IsPrime(Seqint(Intseq(n) cat [3, 3])) ];
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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
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Mathematica
Select[Range[600],PrimeQ[33*10^IntegerLength[#]+#]&] (* Harvey P. Dale, Jul 29 2014 *)
Extensions
More terms from Emeric Deutsch, Sep 02 2005