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A046332 Palindromes with exactly 6 prime factors (counted with multiplicity). 4
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
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
Sequence in context: A205896 A205418 A231709 * A046380 A249228 A154081
KEYWORD
nonn,base
AUTHOR
Patrick De Geest, Jun 15 1998
STATUS
approved

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Last modified March 29 02:13 EDT 2024. Contains 371264 sequences. (Running on oeis4.)