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A074889
Non-palindromic numbers such that the two largest proper divisors are palindromes having at least two digits and no other divisor is a palindrome with at least two digits.
1
524, 928, 1179, 1252, 1292, 1372, 1736, 2101, 2525, 2817, 4103, 4213, 4949, 8327, 8657, 8767, 10109, 10219, 19781, 23711, 25021, 27331, 28841, 34571, 41003, 41204, 45244, 45644, 46243, 47263, 48863, 49684, 50173, 52124, 53303, 53324, 56164, 56323, 56564, 56643
OFFSET
1,1
LINKS
David Consiglio, Jr., Table of n, a(n) for n = 1..212
David Consiglio, Jr., Python Program
EXAMPLE
928 is here since the divisors of 928 are [1, 2, 4, 8, 16, 29, 32, 58, 116, *232*, *464*, 928].
MAPLE
ispali:= proc(n) local L;
L:= convert(n, base, 10); evalb(L = ListTools:-Reverse(L))
end proc:
filter:= proc(n) local D;
if ispali(n) then return false fi;
D:= sort(convert(select(`>=`, numtheory:-divisors(n) minus {n}, 10), list));
nops(D) >= 2 and select(ispali, D) = [D[-2], D[-1]];
end proc:
select(filter, [$1..10^5]); # Robert Israel, Oct 12 2015
MATHEMATICA
tldp[n_]:=Module[{d=Select[Most[Divisors[n]], #>9&]}, Length[d]>1&&d[[-2]]> 9 && !PalindromeQ[n]&&AllTrue[Take[d, -2], PalindromeQ]&&NoneTrue[Drop[d, -2], PalindromeQ]]; Select[Range[57000], tldp] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, May 11 2021 *)
CROSSREFS
Cf. A075407.
Sequence in context: A207356 A207199 A045209 * A249286 A283345 A381619
KEYWORD
base,nonn
AUTHOR
Jason Earls, Sep 13 2002
EXTENSIONS
Corrected and extended by David Consiglio, Jr., Oct 12 2015
STATUS
approved