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 A124706 #12 Apr 30 2025 13:55:04
%S A124706 1,13,37,85,225,593,1609,4409,12217,34105,95817,270569,767325,2184013,
%T A124706 6235693,17852045,51229417,147318953,424429081,1224825209,3539918965,
%U A124706 10244733605,29685367573,86113604309,250061941093,726831403493
%N A124706 Number of base 13 circular n-digit numbers with adjacent digits differing by 1 or less.
%C A124706 [Empirical] a(base,n)=a(base-1,n)+A002426(n+1) for base>=1.int(n/2)+1
%C A124706 a(n) = T(n, 13) 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,..,13}. See theorem 3.3 in Knopfmacher and others, reference in A124696. - _Peter Luschny_, Aug 13 2012
%H A124706 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 A124706 (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 A124706 nonn,base
%O A124706 0,2
%A A124706 _R. H. Hardin_, Dec 28 2006