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A216169 Composite numbers which yield a prime whenever a 0 is inserted anywhere in them, excluding at the beginning or end. 5
49, 119, 121, 133, 161, 169, 203, 253, 299, 301, 319, 323, 403, 407, 473, 493, 511, 539, 551, 581, 611, 667, 679, 713, 869, 901, 913, 943, 1007, 1067, 1079, 1099, 1211, 1273, 1691, 1729, 1799, 1909, 2021, 2047, 2101, 2117, 2359, 2407, 2533, 2717, 2759, 2899 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Paolo P. Lava, Table of n, a(n) for n = 1..1500

EXAMPLE

2359 is not prime but 23509, 23059 and 20359 are all primes.

MAPLE

with(numtheory);

A216169:=proc(q, x)

local a, b, c, i, n, ok;

for n from 10 to q do

if not isprime(n) then

  a:=n; b:=0; while a>0 do b:=b+1; a:=trunc(a/10); od; a:=n; ok:=1;

  for i from 1 to b-1 do c:=a+9*10^i*trunc(a/10^i)+10^i*x;

    if not isprime(c) then ok:=0; break; fi;

  od;

  if ok=1 then print(n); fi;

fi;

od; end:

A216169(1000, 0);

CROSSREFS

Cf. A068673, A068674, A068677, A068679, A069246, A215417, A215419-A215421, A216165-A216168.

Sequence in context: A088868 A044236 A044617 * A090095 A178705 A163245

Adjacent sequences:  A216166 A216167 A216168 * A216170 A216171 A216172

KEYWORD

nonn,base

AUTHOR

Paolo P. Lava, Sep 03 2012

STATUS

approved

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Last modified July 23 22:27 EDT 2017. Contains 289716 sequences.