A107073 Numbers k such that the string 35k is prime.
3, 9, 11, 17, 27, 29, 33, 39, 41, 47, 57, 59, 71, 81, 83, 93, 107, 111, 117, 129, 141, 149, 153, 159, 171, 201, 221, 227, 251, 257, 267, 279, 281, 291, 311, 317, 323, 327, 339, 353, 363, 381, 393, 401, 407, 419, 423, 437, 447, 449, 461, 491, 507, 509, 521, 527
Offset: 1
Examples
If k=47 then 3547 is prime.
Crossrefs
Cf. A032666. - R. J. Mathar, Jan 16 2009
Programs
-
Magma
[ n: n in [1..900] | IsPrime(Seqint(Intseq(n) cat [5, 3])) ]; // Vincenzo Librandi, Feb 03 2011
-
Maple
A055642 := proc(n) max(1,ilog10(n)+1) ; end: cat2 := proc(a,b) a*10^A055642(b)+b ; end: for n from 1 to 1000 do if isprime( cat2(35,n) ) then printf("%d,",n) ; fi; od: # R. J. Mathar, Jan 16 2009
-
Mathematica
Select[Range[600],PrimeQ[FromDigits[Join[{3,5},IntegerDigits[#]]]]&] (* Harvey P. Dale, Jun 06 2015 *)