A132285 Odd palindromes with an even number of digits.

11, 33, 55, 77, 99, 1001, 1111, 1221, 1331, 1441, 1551, 1661, 1771, 1881, 1991, 3003, 3113, 3223, 3333, 3443, 3553, 3663, 3773, 3883, 3993, 5005, 5115, 5225, 5335, 5445, 5555, 5665, 5775, 5885, 5995, 7007, 7117, 7227, 7337, 7447, 7557, 7667, 7777, 7887

Offset: 1

Author

Artur Jasinski, Aug 16 2007

Keywords

• nonn
• base

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..555

Crossrefs

Cf. A005408, A001637, A002113, A132286, A132288.

Programs

Mathematica

monQ[n_]:=Module[{len=IntegerLength[n],idn=IntegerDigits[n]},EvenQ[ len] &&Take[idn,len/2]==Reverse[Take[idn,-len/2]]]; Select[Range[11,9999,2], monQ] (* Harvey P. Dale, Apr 18 2014 *)

PARI

isok(n) = {if (n % 2 == 0, return (0)); d = digits(n); if (#d % 2 == 1, return (0)); for (i=1, #d/2, if (d[i] != d[#d-i+1], return (0));); return (1);} \\ Michel Marcus, Nov 05 2013

Formula

A005408 INTERSECT A001637 INTERSECT A002113. - R. J. Mathar, Aug 22 2007