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URL: https://oeis.org/A135602

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A135602
Right-angled numbers with an internal digit as the vertex.
11
101, 121, 212, 232, 323, 343, 434, 454, 545, 565, 656, 676, 767, 787, 878, 898, 989, 1012, 1210, 1232, 2101, 2123, 2321, 2343, 3212, 3234, 3432, 3454, 4323, 4345, 4543, 4565, 5434, 5456, 5654, 5676, 6545, 6567, 6765, 6787, 7656, 7678, 7876, 7898, 8767, 8789, 8987
OFFSET
1,1
COMMENTS
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.
LINKS
Jens Kruse Andersen, Table of n, a(n) for n = 1..525
EXAMPLE
Illustration using the final term of this sequence:
9 . . . . . . . . . . . . . . . . . 9
. 8 . . . . . . . . . . . . . . . 8 .
. . 7 . . . . . . . . . . . . . 7 . .
. . . 6 . . . . . . . . . . . 6 . . .
. . . . 5 . . . . . . . . . 5 . . . .
. . . . . 4 . . . . . . . 4 . . . . .
. . . . . . 3 . . . . . 3 . . . . . .
. . . . . . . 2 . . . 2 . . . . . . .
. . . . . . . . 1 . 1 . . . . . . . .
. . . . . . . . . 0 . . . . . . . . .
PROG
(Python)
ups = list(tuple(range(i, j)) for i in range(9) for j in range(i+2, 11))
s = set(L[::-1] + R[1:] for L in ups for R in ups if L[0] == R[0])
s |= set(L[:-1] + R[::-1] for L in ups for R in ups if L[-1] == R[-1])
afull = sorted(int("".join(map(str, t))) for t in s if t[0] != 0)
print(afull[:47]) # Michael S. Branicky, Aug 02 2022
KEYWORD
base,fini,full,nonn
AUTHOR
Omar E. Pol, Dec 02 2007
STATUS
approved