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A046332 Palindromes with exactly 6 prime factors (counted with multiplicity). 3
2772, 2992, 6776, 8008, 21112, 21712, 21912, 23632, 23832, 25452, 25752, 25952, 27472, 28782, 29392, 40104, 40304, 40404, 42024, 42924, 44044, 44144, 44744, 44944, 45954, 46764, 46864, 48984, 53235, 54945, 55755, 59895, 60606, 61216 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Chai Wah Wu, Table of n, a(n) for n = 1..5000

MAPLE

N:= 6: # to get all terms of up to N digits

digrev:= proc(n) local L, Ln; L:= convert(n, base, 10); Ln:= nops(L);

add(L[i]*10^(Ln-i), i=1..Ln);

end proc:

Res:= NULL:

for d from 2 to N do

  if d::even then

    m:= d/2;

    Res:= Res, select(numtheory:-bigomega=6,

           [seq](n*10^m + digrev(n), n=10^(m-1)..10^m-1));

  else

    m:= (d-1)/2;

    Res:= Res, select(numtheory:-bigomega=6,

           [seq](seq(n*10^(m+1)+y*10^m+digrev(n), y=0..9), n=10^(m-1)..10^m-1));

  fi

od:

map(op, [Res]); # Robert Israel, Dec 23 2014

PROG

(Python)

from sympy import factorint

def palQgen10(l): # generator of palindromes in base 10 of length <= 2*l

....if l > 0:

........yield 0

........for x in range(1, l+1):

............for y in range(10**(x-1), 10**x):

................s = str(y)

................yield int(s+s[-2::-1])

............for y in range(10**(x-1), 10**x):

................s = str(y)

................yield int(s+s[::-1])

A046332_list = [x for x in palQgen10(4) if sum(list(factorint(x).values())) == 6]

# Chai Wah Wu, Dec 21 2014

CROSSREFS

Cf. A046306, A046319.

Sequence in context: A205896 A205418 A231709 * A046380 A249228 A154081

Adjacent sequences:  A046329 A046330 A046331 * A046333 A046334 A046335

KEYWORD

nonn,base

AUTHOR

Patrick De Geest, Jun 15 1998

STATUS

approved

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Last modified May 23 19:46 EDT 2017. Contains 286926 sequences.