

A083684


Numbers n such that there is no nonnegative integer m such that m < n*prime(n) and the concatenated decimal number fp(n,m) = prime(1).m.prime(2).m. ... .prime(n1).m.prime(n) is prime.


1



3, 10, 16, 28, 34, 40, 46, 52, 70, 76, 82, 88, 97, 103, 121, 127, 136, 163, 166, 169, 175, 187, 199, 205, 211, 217, 220, 235, 250, 262, 268
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OFFSET

1,1


COMMENTS

For each m, fp(1,m)=2 is prime so 1 is not in the sequence.
If n == 1 (mod 3) and 3 divides 2+3+5+...+prime(n) then n
is in the sequence. I conjecture that 3 is the only term of the sequence which is not of this form.


LINKS

Table of n, a(n) for n=1..31.


EXAMPLE

fp(2,2) = 2.2.3 = 223 is prime and 2 < 2*prime(2) so 2 isn't in the sequence. Also for each m, 5 divides fp(3,m) = 2.m.3.m.5 so fp(3,m) is composite and we deduce that 3 is in the sequence.


CROSSREFS

Cf. A082549, A083677.
Sequence in context: A278041 A063209 A063109 * A141497 A059911 A160375
Adjacent sequences: A083681 A083682 A083683 * A083685 A083686 A083687


KEYWORD

nonn,base


AUTHOR

Farideh Firoozbakht, Jun 15 2003


EXTENSIONS

Corrected and edited by Farideh Firoozbakht, Nov 04 2013


STATUS

approved



