This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A308199 #17 Jul 20 2022 08:52:31
%S A308199 0,4,7,11,13,17,20,24,28,31,35,37,41,44,48,51,55,57,61,64,68,72,75,79,
%T A308199 81,85,88,92,94,98,101,105,109,112,116,118,122,125,129,132,136,138,
%U A308199 142,145,149,153,156,160,162,166,169,173,177,180,184,186,190,193,197,200,204,206,210,213,217,221,224,228
%N A308199 The tribonacci representation of a(n) is obtained by appending 0,0 to the tribonacci representation of n (cf. A278038).
%C A308199 From _Michel Dekking_, Oct 06 2019: (Start)
%C A308199 If w is a binary vector not containing 111, then w00 and w01 are also binary vectors not containing 111. So a(n) = A278040(n) - 1.
%C A308199 This sequence gives the positions of the word ab in the tribonacci word t, when t is given offset 0.
%C A308199 This sequence is the compound sequence A278039(A278039) of the three sequences A278039, A278040, A278041, which are the building blocks of the tribonacci world with offset 0. (End)
%F A308199 From _Michel Dekking_, Oct 06 2019: (Start)
%F A308199 a(n) = Sum_{k=1..n-1} d(k), where d is the tribonacci word on the alphabet {4,3,2}.
%F A308199 a(n) = A003144(A003144(n)) - 1. (End)
%e A308199 u = abacabaabacaba.., then u(0)u(1) = ab, u(4)u(5) = ab, u(7)u(8) = ab, u(11)u(12) = ab.
%Y A308199 Cf. A278038, A278039, A278040, A278041, A308200.
%Y A308199 Essentially partial sums of A276789.
%K A308199 nonn,base
%O A308199 0,2
%A A308199 _N. J. A. Sloane_, Jun 23 2019