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

1,1

Links

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

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 *)

Crossrefs

Cf. A016041.

Sequence in context: A225461 A172181 A063139 * A097636 A179384 A225513

Adjacent sequences: A163167 A163168 A163169 * A163171 A163172 A163173

Keyword

base,nonn

Author

Leroy Quet, Jul 22 2009

Extensions

Extended by Emeric Deutsch, Jul 24 2009

Status

approved