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 A124783 #12 Apr 30 2025 14:04:51
%S A124783 1,28,82,190,510,1358,3724,10304,28822,81190,230112,655364,1874160,
%T A124783 5378128,15479098,44666150,129178822,374342918,1086721216,3159778004,
%U A124783 9200609500,26824994540,78302400478,228812026154,669286986808
%N A124783 Number of base 28 circular n-digit numbers with adjacent digits differing by 1 or less.
%C A124783 [Empirical] a(base,n)=a(base-1,n)+A002426(n+1) for base>=1.int(n/2)+1
%C A124783 a(n) = T(n, 28) 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,..,28}. See theorem 3.3 in Knopfmacher and others, reference in A124696. - _Peter Luschny_, Aug 13 2012
%H A124783 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 A124783 (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 A124783 nonn,base
%O A124783 0,2
%A A124783 _R. H. Hardin_, Dec 28 2006