A217373 Numbers n the representation of which in base 3 ends in 2*k or 2*k+1 zeros, where k is odd.

9, 18, 27, 36, 45, 54, 63, 72, 90, 99, 108, 117, 126, 135, 144, 153, 171, 180, 189, 198, 207, 216, 225, 234, 252, 261, 270, 279, 288, 297, 306, 315, 333, 342, 351, 360, 369, 378, 387, 396, 414, 423, 432, 441, 450, 459, 468, 477, 495, 504, 513, 522, 531, 540

Offset: 1

Author

Vladimir Shevelev, Mar 18 2013

Keywords

• nonn
• easy

Comments

Or numbers having infinitary divisor 9, or the same having factor 9 in their Fermi-Dirac factorization as product of distinct terms of A050376.

Links

• Peter J. C. Moses, Table of n, a(n) for n = 1..10000
• Index entries for 3-automatic sequences.

Crossrefs

Cf. A145204, A217319, A036554, A050376.

Programs

Mathematica

Select[Map[# Boole[IntegerQ[(1/4 (1+#))]||IntegerQ[(1/4 (2+#))]&[Length[Last[Split[IntegerDigits[#,3]]]]]]&,Range[3,5000,3]],#>0&] (* Peter J. C. Moses, Mar 20 2013 *)

Formula

a(n)/(10*n) tends to 1, as n goes to infinity.