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A075810
Palindromic odd squarefree numbers with an even number of distinct prime factors.
0
1, 33, 55, 77, 111, 141, 161, 303, 323, 393, 505, 515, 535, 545, 565, 707, 717, 737, 767, 939, 949, 959, 979, 989, 1111, 1441, 1661, 1991, 3003, 3113, 3223, 3443, 3883, 5005, 5115, 7117, 7447, 7997, 9119, 9229, 9449, 10001, 10101, 10401, 10801, 10901
OFFSET
1,2
EXAMPLE
77=7*11 and 3003=3*7*11*13 are palindromic, odd, squarefree and have an even number of prime factors.
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 11000 by 2 do if test(n) then a := [op(a), n]; end; od; a;
MATHEMATICA
psdQ[n_]:=Module[{idn=IntegerDigits[n]}, idn==Reverse[idn]&&SquareFreeQ[n] && EvenQ[PrimeNu[n]]]; Select[Range[1, 11001, 2], psdQ] (* Harvey P. Dale, Aug 21 2011 *)
CROSSREFS
Cf. A056913.
Sequence in context: A242957 A024628 A061864 * A132288 A242605 A351396
KEYWORD
nonn,base
AUTHOR
Jani Melik, Oct 13 2002
EXTENSIONS
Edited by Dean Hickerson, Oct 21 2002
STATUS
approved