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A319972 a(n) = A003146(A003146(n)). 16
24, 68, 105, 149, 173, 217, 254, 298, 342, 379, 423, 447, 491, 528, 572, 609, 653, 677, 721, 758, 802, 846, 883, 927, 951, 995, 1032, 1076, 1100, 1144, 1181, 1225, 1269, 1306, 1350, 1374, 1418, 1455, 1499, 1536, 1580, 1604, 1648, 1685, 1729, 1773, 1810, 1854 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

By analogy with the Wythoff compound sequences A003622 etc., the nine compounds of A003144, A003145, A003146 might be called the tribonacci compound sequences. They are A278040, A278041, and A319966-A319972.

This sequence gives the positions of the word cabac in the tribonacci word t = abacabaa..., fixed point of the morphism a->ab, b->ac, c->a.  This follows from the fact that the positional sequences of cabaa, cabab and cabac give a splitting of the positional sequence of the word caba (the unique word in t with prefix the letter c), and that the three sets CA(N), CB(N) and CC(N), give a splitting of the set C(N), where A := A003144, B := A003145, C := A003146. Here N is the set of positive integers. - Michel Dekking, Apr 09 2019

LINKS

Rémy Sigrist, Table of n, a(n) for n = 1..10000

Elena Barcucci, Luc Belanger and Srecko Brlek, On tribonacci sequences, Fib. Q., 42 (2004), 314-320. Compare page 318.

FORMULA

a(n) = A003146(A003146(n)).

a(n) = 6*A003144(n) + 7*A003145(n) + 4*n = 7*A278040(n-1) + 6*A278039(n-1) + 4*n + 13, n >= 1. For a proof see the W. Lang link in A278040, Proposition 9, eq. (56). - Wolfdieter Lang, Apr 11 2019

CROSSREFS

Cf. A003144, A003145, A003146, A003622, A278039, A278040, A278041, and A319966-A319972.

Sequence in context: A039331 A043934 A087406 * A304157 A051876 A069174

Adjacent sequences:  A319969 A319970 A319971 * A319973 A319974 A319975

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Oct 05 2018

EXTENSIONS

More terms from Rémy Sigrist, Oct 16 2018

STATUS

approved

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Last modified February 26 09:45 EST 2020. Contains 332277 sequences. (Running on oeis4.)