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%I #15 Aug 03 2022 02:33:55
%S 101,121,212,232,323,343,434,454,545,565,656,676,767,787,878,898,989,
%T 1012,1210,1232,2101,2123,2321,2343,3212,3234,3432,3454,4323,4345,
%U 4543,4565,5434,5456,5654,5676,6545,6567,6765,6787,7656,7678,7876,7898,8767,8789,8987
%N Right-angled numbers with an internal digit as the vertex.
%C The structure of digits represents a right angle. The vertex is an internal digit. In the graphic representation the points are connected by imaginary line segments from left to right. This sequence is finite. The final term has 19 digits: 9876543210123456789.
%H Jens Kruse Andersen, <a href="/A135602/b135602.txt">Table of n, a(n) for n = 1..525</a>
%e Illustration using the final term of this sequence:
%e 9 . . . . . . . . . . . . . . . . . 9
%e . 8 . . . . . . . . . . . . . . . 8 .
%e . . 7 . . . . . . . . . . . . . 7 . .
%e . . . 6 . . . . . . . . . . . 6 . . .
%e . . . . 5 . . . . . . . . . 5 . . . .
%e . . . . . 4 . . . . . . . 4 . . . . .
%e . . . . . . 3 . . . . . 3 . . . . . .
%e . . . . . . . 2 . . . 2 . . . . . . .
%e . . . . . . . . 1 . 1 . . . . . . . .
%e . . . . . . . . . 0 . . . . . . . . .
%o (Python)
%o ups = list(tuple(range(i, j)) for i in range(9) for j in range(i+2, 11))
%o s = set(L[::-1] + R[1:] for L in ups for R in ups if L[0] == R[0])
%o s |= set(L[:-1] + R[::-1] for L in ups for R in ups if L[-1] == R[-1])
%o afull = sorted(int("".join(map(str, t))) for t in s if t[0] != 0)
%o print(afull[:47]) # _Michael S. Branicky_, Aug 02 2022
%Y Cf. A134810, A134853, A134941, A134970, A135641, A135642, A135643, A135600, A135601, A135603.
%K base,fini,full,nonn
%O 1,1
%A _Omar E. Pol_, Dec 02 2007
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