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A046394 Palindromes with exactly 4 distinct prime factors. 1
858, 2002, 2442, 3003, 4774, 5005, 5115, 6666, 10101, 15351, 17871, 22422, 22722, 24242, 26562, 26962, 28482, 35853, 36363, 41314, 43734, 43834, 45654, 47874, 49494, 49794, 49894, 51015, 51315, 51415, 53535, 53835, 53935, 56865, 58485 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

MAPLE

filter:= proc(n) local F;

  F:= ifactors(n)[2];

  nops(F)=4 and max(map(t->t[2], F))=1

end proc:

makepali:= proc(n, d) local L;

  L:= convert(n, base, 10);

  if d::even then 10^(d/2)*n + add(L[i]*10^(d/2-i), i=1..d/2)

  else 10^((d-1)/2)*n + add(L[i]*10^((d+1)/2-i), i=2..(d+1)/2)

  fi

end proc:

select(filter, [seq(seq(makepali(x, d),

   x=10^ceil(d/2-1)..10^ceil(d/2)-1), d=1..6)]); # Robert Israel, Jun 05 2018

CROSSREFS

Cf. A046330, A046410.

Sequence in context: A251453 A087002 A256743 * A163304 A252237 A284074

Adjacent sequences:  A046391 A046392 A046393 * A046395 A046396 A046397

KEYWORD

nonn,base

AUTHOR

Patrick De Geest, Jun 15 1998

STATUS

approved

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Last modified March 23 18:13 EDT 2019. Contains 321433 sequences. (Running on oeis4.)