A046332 Palindromes with exactly 6 prime factors (counted with multiplicity).
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
Offset: 1
Links
- Chai Wah Wu, Table of n, a(n) for n = 1..5000
Crossrefs
Programs
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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 -
PARI
A046332_upto(N, start=1, num_fact=6)={ my(L=List()); while(N >= start = nxt_A002113(start), bigomega(start)==num_fact && listput(L, start)); L} \\ M. F. Hasler, Jun 06 2024
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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