A075800 Palindromic numbers which are products of an odd number of distinct primes.
2, 3, 5, 7, 11, 66, 101, 131, 151, 181, 191, 222, 282, 313, 353, 373, 383, 434, 474, 494, 555, 595, 606, 646, 727, 757, 777, 787, 797, 919, 929, 969, 1001, 1221, 1551, 1771, 2222, 2882, 3333, 3553, 4334, 4994, 5335, 5555, 5665, 5885, 5995, 6006, 6226, 6446, 6886
Offset: 1
Examples
191 is palindromic and prime, 222=2*3*37 is palindromic and a product of 3 distinct primes.
Links
- Chai Wah Wu, Table of n, a(n) for n = 1..10000
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