

A244397


Consider a number n with m decimal digits, m>1. The sequence lists the numbers n such that the prefix of length m1 and the suffix of length m1 have both the same distinct prime divisors.


0



22, 24, 28, 33, 39, 42, 44, 48, 55, 66, 77, 82, 84, 88, 93, 99, 111, 124, 164, 222, 248, 333, 444, 526, 548, 555, 666, 724, 777, 842, 888, 999, 1111, 1248, 1664, 2162, 2222, 2500, 2855, 3200, 3333, 3600, 3748, 4324, 4444, 4864, 5042, 5128, 5555, 5768, 5882
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OFFSET

1,1


COMMENTS

Let x(0)x(1)...x(q1)x(q) denote the decimal expansion of a number n. The sequence lists the numbers n such that the prefix p = x(0)x(1)...x(q1) and the suffix x(1)...x(q1)x(q) have the same prime distinct divisors.


LINKS

Table of n, a(n) for n=1..51.


EXAMPLE

3748 is in the sequence because 374 and 748 have the same prime divisors: {2,11,17).


MAPLE

with(numtheory):
for n from 10 to 10000 do:
x:=convert(n, base, 10):n1:=nops(x):
s1 := n mod 10^ilog10(n):
s2:=(nirem(n, 10))/10:
x1:=factorset(s1):x2:=factorset(s2):
if x1 = x2 and x1 <>{}
then
printf(`%d, `, n):
else
fi:
od:


CROSSREFS

Cf. A244394.
Sequence in context: A067189 A030593 A235807 * A138603 A181454 A155911
Adjacent sequences: A244394 A244395 A244396 * A244398 A244399 A244400


KEYWORD

nonn,base


AUTHOR

Michel Lagneau, Jun 27 2014


STATUS

approved



