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 A124726 #12 Apr 30 2025 14:03:50
%S A124726 1,27,79,183,491,1307,3583,9911,27715,78051,221159,629711,1800371,
%T A124726 5165187,14862871,42878543,123982195,359207987,1042568407,3030781151,
%U A124726 8823230131,25719643811,75061264951,219298798031,641338650427
%N A124726 Number of base 27 circular n-digit numbers with adjacent digits differing by 1 or less.
%C A124726 [Empirical] a(base,n)=a(base-1,n)+A002426(n+1) for base>=1.int(n/2)+1
%C A124726 a(n) = T(n, 27) where T(n, k) = Sum_{j=1..k} (1+2*cos(j*Pi/(k+1)))^n. These are the number of smooth cyclic words of length n over the alphabet {1,2,..,27}. See theorem 3.3 in Knopfmacher and others, reference in A124696. - _Peter Luschny_, Aug 13 2012
%H A124726 OEIS Wiki, <a href="/wiki/Number_of_base_k_circular_n-digit_numbers_with_adjacent_digits_differing_by_d_or_less">Number of base k circular n-digit numbers with adjacent digits differing by d or less</a>
%o A124726 (S/R) stvar $[N]:(0..M-1) init $[]:=0 asgn $[]->{*} kill +[i in 0..N-1](($[i]`-$[(i+1)mod N]`>1)+($[(i+1)mod N]`-$[i]`>1))
%K A124726 nonn,base
%O A124726 0,2
%A A124726 _R. H. Hardin_, Dec 28 2006
%E A124726 Edited by _Charles R Greathouse IV_, Aug 05 2010