A075799 Palindromic numbers which are products of an even number of distinct primes.
1, 6, 22, 33, 55, 77, 111, 141, 161, 202, 262, 303, 323, 393, 454, 505, 515, 535, 545, 565, 626, 707, 717, 737, 767, 818, 838, 858, 878, 898, 939, 949, 959, 979, 989, 1111, 1441, 1661, 1991, 2002, 2442, 3003, 3113, 3223, 3443, 3883, 4774, 5005, 5115, 6666, 7117, 7447
Offset: 1
Examples
1, 111=3*37 and 858=2*3*11*13 are palindromic and products of an even number of distinct primes.
Links
- Paolo Xausa, Table of n, a(n) for n = 1..1000
Programs
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Maple
test := proc(n) local d; d := convert(n,base,10); return ListTools[Reverse](d)=d and numtheory[mobius](n)=1; end; a := []; for n from 1 to 7000 do if test(n) then a := [op(a),n]; end; od; a;
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Mathematica
Select[Range[10000], PalindromeQ[#] && MoebiusMu[#] == 1 &] (* Paolo Xausa, Mar 10 2025 *)
Extensions
Edited by Dean Hickerson, Oct 21 2002