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Triangle-shaped numbers.
2

%I #7 Aug 03 2022 02:33:51

%S 100,101,102,103,104,105,106,107,108,109,110,112,113,114,115,116,117,

%T 118,119,120,121,122,124,125,126,127,128,129,130,131,132,133,134,136,

%U 137,138,139,140,141,142,143,144,145,146,148,149,150,151

%N Triangle-shaped numbers.

%C The structure of digits represents a triangle. Three digits are the vertex. In the graphic representation the points are connected by imaginary line segments. All 3-digit numbers are terms of this sequence, except for the straight-line numbers A135643. For 4 or more digits the terms are 1000, 1011, 1012, 1024, 1034, 1036, ...

%e The triangle number 1024:

%e . . . 4

%e . . . .

%e . . 2 .

%e 1 . . .

%e . 0 . .

%Y Cf. A134810, A135600, A135601, A135602, A135603, A135643.

%Y Not to be confused with the triangular numbers, A000217!

%K base,nonn

%O 1,1

%A _Omar E. Pol_, Dec 05 2007