A075813 Palindromic even numbers with exactly 2 prime factors (counted with multiplicity). Equivalently, palindromic numbers of the form 2*p with p prime.
4, 6, 22, 202, 262, 454, 626, 818, 838, 878, 898, 20302, 20602, 22322, 22522, 22622, 22822, 24142, 24842, 26662, 26762, 28682, 41014, 41414, 41614, 41714, 43034, 43234, 43534, 43634, 45454, 45554, 45754, 47074, 47374, 47774, 49094, 49394
Offset: 1
Examples
4=2^2, 6=2*3 and 22=2*11 are palindromic, even and have exactly 2 prime factors.
Programs
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Maple
test := proc(n) local d; d := convert(n,base,10); return ListTools[Reverse](d)=d and numtheory[bigomega](n)=2; end; a := []; for n from 2 to 50000 by 2 do if test(n) then a := [op(a),n]; end; od; a;
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Mathematica
Select[Range[50000],EvenQ[#]&&PalindromeQ[#]&&PrimeOmega[#]==2&] (* Harvey P. Dale, Oct 16 2024 *)
Extensions
Edited by Dean Hickerson, Oct 21 2002