This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A135600 #21 Dec 18 2024 19:07:47 %S A135600 100,101,102,103,104,105,106,107,108,109,110,111,112,113,114,115,116, %T A135600 117,118,119,120,121,122,123,124,125,126,127,128,129,130,131,132,133, %U A135600 134,135,136,137,138,139,140,141,142,143,144,145,146,147 %N A135600 Angled numbers with an internal digit as the vertex. %C A135600 The structure of digits represents an angle. The vertex is an internal digit. In the graphic representation the points are connected by imaginary line segments from left to right. The last acute-angled number of this sequence has 14 digits: 98765432102468. The last right-angled number of this sequence has 19 digits: 9876543210123456789. All 3-digit numbers are terms of this sequence. Next terms are 1000, 1012, 1024, 1036, 1048, 1110, 1111, 1112, 1113, 1114, .... %C A135600 For each k >= 20, there are 363 k-digit terms: 354 obtuse-angled and 9 straight-angled.- _Michael S. Branicky_, Aug 03 2022 %H A135600 David A. Corneth, <a href="/A135600/b135600.txt">Table of n, a(n) for n = 1..10910</a> %H A135600 David A. Corneth, <a href="/A135600/a135600.gp.txt">PARI program</a> %e A135600 The acute-angled number 12342 (see A135601): %e A135600 . . . . . %e A135600 . . . 4 . %e A135600 . . 3 . . %e A135600 . 2 . . 2 %e A135600 1 . . . . %e A135600 The right-angled number 12343 (see A135602): %e A135600 . . . . . %e A135600 . . . 4 . %e A135600 . . 3 . 3 %e A135600 . 2 . . . %e A135600 1 . . . . %e A135600 The obtuse-angled number 12344 (see A135603): %e A135600 . . . . . %e A135600 . . . 4 4 %e A135600 . . 3 . . %e A135600 . 2 . . . %e A135600 1 . . . . %e A135600 The straight-angled (or straight-line) number 12345 (see A135643): %e A135600 . . . . 5 %e A135600 . . . 4 . %e A135600 . . 3 . . %e A135600 . 2 . . . %e A135600 1 . . . . %o A135600 (PARI) \\ See PARI link. _David A. Corneth_, Aug 02 2022 %o A135600 (Python) %o A135600 from itertools import count, islice %o A135600 def agen(): %o A135600 seeds = [k for k in range(100, 1000)] %o A135600 for digits in count(4): %o A135600 yield from sorted(seeds) %o A135600 new, pow10 = set(), 10**(digits-1) %o A135600 for q in seeds: %o A135600 d = list(map(int, str(q))) %o A135600 e1, e2 = d[0] - (d[1]-d[0]), d[-1] + (d[-1]-d[-2]) %o A135600 if 9 >= e1 > 0: new.add(e1*pow10 + q) %o A135600 if 9 >= e2 >= 0: new.add(10*q + e2) %o A135600 seeds = new %o A135600 print(list(islice(agen(), 50))) # _Michael S. Branicky_, Aug 03 2022 %Y A135600 Cf. A134810, A134853, A134941, A134970, A135641, A135642, A135643, A135601, A135602, A135603. %K A135600 nonn,easy,base %O A135600 1,1 %A A135600 _Omar E. Pol_, Dec 02 2007