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Nonnegative numbers in (3*A005836 - 1) [A005836 are the numbers with base representation containing no 2].
4

%I #18 Jun 04 2022 04:31:16

%S 2,8,11,26,29,35,38,80,83,89,92,107,110,116,119,242,245,251,254,269,

%T 272,278,281,323,326,332,335,350,353,359,362,728,731,737,740,755,758,

%U 764,767,809,812,818,821,836,839,845,848,971,974,980,983,998,1001,1007,1010

%N Nonnegative numbers in (3*A005836 - 1) [A005836 are the numbers with base representation containing no 2].

%C Numbers k such that the Motzkin number A001006(k) == 2 (mod 3).

%H Amiram Eldar, <a href="/A089118/b089118.txt">Table of n, a(n) for n = 1..10000</a>

%H Rob Burns, <a href="https://arxiv.org/abs/1611.04910">Asymptotic density of Motzkin numbers modulo small primes</a>, arXiv:1611.04910 [math.NT], 2016.

%t (* m = MotzkinNumber *) m[0] = 1; m[n_] := m[n] = m[n - 1] + Sum[ m[k]*m[n - 2 - k], {k, 0, n - 2}]; Select[ Range[1010], Mod[m[#], 3] == 2 &] (* _Jean-François Alcover_, Jul 10 2013 *)

%t Select[3*Range[350] - 1, DigitCount[# + 1, 3, 2] == 0 &] (* _Amiram Eldar_, Jun 04 2022 *)

%Y Cf. A005836, A001006, A082575, A089119.

%K nonn,base

%O 1,1

%A _Emeric Deutsch_ and _Bruce E. Sagan_, Dec 05 2003

%E Offset corrected to 1 by _Jean-François Alcover_, Jun 23 2016