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A228856 Nodes of tree generated as follows: (1,2) is an edge, and if (x,y) is an edge, then (y,y+x), (y,2y+x), and (y,3y+x) are edges. 5
1, 2, 3, 5, 7, 8, 9, 11, 12, 13, 14, 16, 17, 18, 19, 21, 22, 23, 25, 26, 27, 29, 30, 31, 33, 34, 35, 36, 37, 39, 41, 43, 44, 45, 46, 47, 49, 50, 52, 53, 55, 56, 57, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 73, 74, 75, 76, 77, 79, 80, 81, 83, 84 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Ivan Neretin, Table of n, a(n) for n = 1..10000

EXAMPLE

Taking the first generation of edges of the tree to be G(1) = {(1,2)}, the edge (1,2) grows G(2) = {(2,3), (2,5), (2,7)}, which grows G(3) = {(3,5), (3,8), (3,11), (5,7), 5,12), 5,17), (7,9), (7,16), (7,23)}, ... Expelling duplicate nodes and sorting leave {1,2,3,5,7,8,9,...}.

MATHEMATICA

f[x_, y_] := {{y, x + y}, {y, x + 2 y}}; x = 2; y = 3; t = {{x, y}};

u = Table[t = Flatten[Map[Apply[f, #] &, t], 1], {12}]; v = Flatten[u];

w = Flatten[Prepend[Table[v[[2 k]], {k, 1, Length[v]/2}], {x, y}]];

Sort[Union[w]]

CROSSREFS

Cf. A141832, A228853, A228854, A228856.

Sequence in context: A226811 A227802 A329780 * A274688 A053661 A171944

Adjacent sequences:  A228853 A228854 A228855 * A228857 A228858 A228859

KEYWORD

nonn,easy

AUTHOR

Clark Kimberling, Sep 05 2013

STATUS

approved

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Last modified May 9 15:34 EDT 2021. Contains 343742 sequences. (Running on oeis4.)