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 A299792 #92 Feb 16 2025 08:33:53 %S A299792 0,11,22,33,44,55,66,77,88,99,111,222,333,444,555,666,777,888,999, %T A299792 1001,1010,1012,1023,1034,1045,1056,1067,1078,1089,1100,1111,1122, %U A299792 1133,1144,1155,1166,1177,1188,1199,1210,1212,1221,1232,1243,1254,1265,1276,1287,1298,1313 %N A299792 Numbers k such that A177894(k) = 0. %C A299792 A one-digit number a is in this sequence if and only if a = 0. %C A299792 A two-digit number ab is in this sequence if and only if a = b. %C A299792 A three-digit number abc is in this sequence if and only if a = b = c. %C A299792 A four-digit number abcd is in this sequence if and only if a + c = b + d or (a = c and b = d) %C A299792 A239019 is trivially a subsequence (because the corresponding circular matrices each contains at least two identical rows or columns). {a(n)} \ A239019 is given as A317291. %H A299792 Paolo Xausa, <a href="/A299792/b299792.txt">Table of n, a(n) for n = 1..10000</a> %H A299792 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/CirculantMatrix.html">Circulant Matrix</a> %H A299792 Wikipedia, <a href="http://en.wikipedia.org/wiki/Circulant_matrix">Circulant matrix</a> %e A299792 1452 is a term because the value of the following determinant is 0: %e A299792 | 1 4 5 2 | %e A299792 | 4 5 2 1 | %e A299792 | 5 2 1 4 | %e A299792 | 2 1 4 5 | %t A299792 A299792Q[k_] := k == 0 || Det[NestList[RotateLeft, IntegerDigits[k], IntegerLength[k]-1]] == 0; Select[Range[0, 2000], A299792Q] (* _Paolo Xausa_, Mar 11 2024 *) %o A299792 (PARI) for(n=0, 1500, if(!A177894(n), print1(n, ", "))) \\ See A177894 for its program %Y A299792 Cf. A177894, A239019, A317291. %K A299792 nonn,base %O A299792 1,2 %A A299792 _Jianing Song_, Jan 21 2019