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 A380714 #32 Apr 15 2025 15:04:19
%S A380714 0,2,6,3,2,3,6,2,0,90,11,33,57,83,12,42,74,9,45,83,24,66,11,57,6,56,9,
%T A380714 63,20,78,39,2,66,33,2,72,45,20,96,75,56,39,24,11,0,90,83,78,75,74,75,
%U A380714 78,83,90,0,11,24,39,56,75,96,20,45,72,2,33,66
%N A380714 a(n) = n*(n-1) mod (10^m-1) where m is the number of decimal digits in n.
%C A380714 a(n) = 0 if and only if n is a Kaprekar number (A053816).
%H A380714 Giorgos Kalogeropoulos, <a href="/A380714/b380714.txt">Table of n, a(n) for n = 1..9999</a>
%F A380714 a(n) = A002378(n-1) mod A002283(A055642(n)).
%p A380714 a:= n-> n*(n-1) mod (10^length(n)-1):
%p A380714 seq(a(n), n=1..67); # _Alois P. Heinz_, Mar 27 2025
%t A380714 Table[Mod[n(n-1), 10^IntegerLength@n - 1], {n,67}]
%o A380714 (Python)
%o A380714 def a(n): return n*(n-1)%(10**len(str(n))-1)
%o A380714 print([a(n) for n in range(1, 68)]) # _Michael S. Branicky_, Mar 27 2025
%Y A380714 Cf. A002283, A002378, A053816, A055642.
%K A380714 nonn,base,look
%O A380714 1,2
%A A380714 _Giorgos Kalogeropoulos_, Mar 27 2025