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 A326639 #10 Dec 06 2019 21:45:32 %S A326639 1000,10000,1001,1003,1004,1035,1061,1127,1184,1095,1200,2300,2050, %T A326639 2370,1280,1300,1030,3040,1530,3950,4390,4080,5030,1040,6000,1600, %U A326639 3600,7200,2700,8300,3800,1800,1002,1129,1936,1649,1296,1799,1090,1010,1012,1020,1038,1008,1005,1006,1007,1011,1013,1014,1105,1120,1031 %N A326639 For any k, the cumulative sum a(1) + a(2) + a(3) + ... + a(k) shares at least four digits with a(k). Lexicographically first sequence of positive integers without duplicate terms having this property. %H A326639 Jean-Marc Falcoz, <a href="/A326639/b326639.txt">Table of n, a(n) for n = 1..5001</a> %e A326639 Here are the first terms of the sequence: %e A326639 1000,10000,1001,1003,1004,1035,1061,1127,1184,... %e A326639 and here are the cumulative sums: %e A326639 1000,11000,12001,13004,14008,15043,16104,17231,18415,... %e A326639 If we align a(n) and its cumulative sum, we see that at least four digits are shared: %e A326639 1000,10000, 1001, 1003, 1004, 1035 ,1061, 1127, 1184,... %e A326639 1000,11000,12001,13004,14008,15043,16104,17231,18415,... %Y A326639 Cf. A309151 (no digit is shared by the cumulative sum instead of four digits here), A316914 (one digit is shared), A316915 (two digits shared), A326638 (three digits shared), A326640 (five digits shared). %K A326639 base,nonn %O A326639 1,1 %A A326639 _Eric Angelini_ and _Jean-Marc Falcoz_, Jul 15 2019