A163170 Odd composite integers that are palindromes when written in binary.

9, 15, 21, 27, 33, 45, 51, 63, 65, 85, 93, 99, 119, 129, 153, 165, 189, 195, 219, 231, 255, 273, 297, 325, 341, 365, 381, 387, 403, 427, 455, 471, 495, 511, 513, 561, 585, 633, 645, 693, 717, 765, 771, 819, 843, 891, 903, 951, 975, 1023, 1025, 1057, 1105, 1137

Offset: 1

Author

Leroy Quet, Jul 22 2009

Keywords

• base
• nonn

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A016041.

Programs

Maple

rev := proc (n) local nn: nn := convert(n, base, 10): add(nn[j]*10^(nops(nn)-j), j = 1 .. nops(nn)) end proc: a := proc (n) local n2: n2 := convert(n, binary): if 1 < n and `mod`(n, 2) = 1 and isprime(n) = false and rev(n2) = n2 then n else end if end proc: seq(a(n), n = 1 .. 1500); # Emeric Deutsch, Jul 24 2009

Mathematica

Select[Range[1,1201,2],CompositeQ[#]&&IntegerDigits[#,2]==Reverse[IntegerDigits[#,2]]&] (* Harvey P. Dale, Dec 28 2024 *)

Extensions

Extended by Emeric Deutsch, Jul 24 2009