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A083815 Semiprimes whose prime factors are distinct and the reversal of one factor is equal to the other. 7
403, 1207, 2701, 7663, 35143, 75007, 117907, 127087, 140209, 173809, 197209, 247021, 257821, 342127, 382387, 643063, 692443, 743623, 1226221, 1341331, 1626151, 1698661, 1739161, 2073991, 2138791, 2528611, 2561011, 3321133 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Products of emirp pairs, sorted. - Lekraj Beedassy, Jan 10 2008

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

EXAMPLE

a(2)= 1207 = 17 * 71.

MAPLE

revdigs:= proc(n) local i, L;

  L:= convert(n, base, 10);

  add(L[-i]*10^(i-1), i=1..nops(L))

end proc:

f:= proc(p) local r;

  if not isprime(p) then return NULL fi;

  r:= revdigs(p);

  if r > p and isprime(r) then r*p fi

end proc:

sort(map(f, [seq(i, i=13..9999, 2)])); # Robert Israel, Dec 26 2018

CROSSREFS

Cf. A001358, A006567, A109308.

Sequence in context: A097740 A325151 A213605 * A250893 A261857 A165808

Adjacent sequences:  A083812 A083813 A083814 * A083816 A083817 A083818

KEYWORD

base,nonn

AUTHOR

Jason Earls, Jun 17 2003

EXTENSIONS

More terms from Ray Chandler, Jul 22 2003

STATUS

approved

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Last modified July 9 00:55 EDT 2020. Contains 335537 sequences. (Running on oeis4.)