A075810 Palindromic odd squarefree numbers with an even number of distinct prime factors.

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

Links

Table of n, a(n) for n=1..46.

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

Adjacent sequences: A075807 A075808 A075809 * A075811 A075812 A075813

Keyword

nonn,base

Author

Jani Melik, Oct 13 2002

Extensions

Edited by Dean Hickerson, Oct 21 2002

Status

approved