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 A124948 #12 Apr 30 2025 14:49:45
%S A124948 1,20,94,350,1522,6670,29992,136548,628362,2914622,13606624,63855108,
%T A124948 300982084,1423941500,6758032522,32161829650,153427657050,
%U A124948 733475019582,3513035370640,16854198764892,80981882536292,389635048394172
%N A124948 Number of base 20 circular n-digit numbers with adjacent digits differing by 2 or less.
%C A124948 [Empirical] a(base,n)=a(base-1,n)+A005191(n+1) for base>=2.int(n/2)+1.
%C A124948 See A285280 for confirmation of linear recurrence and code to produce sequence. - _Ray Chandler_, Aug 12 2023.
%H A124948 Ray Chandler, <a href="/A124948/b124948.txt">Table of n, a(n) for n = 0..99</a>
%H A124948 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>
%H A124948 <a href="/index/Rec#order_20">Index entries for linear recurrences with constant coefficients</a>, signature (20, -153, 510, -324, -2336, 4689, 2886, -12910, 616, 16708, -3968, -11524, 3200, 4214, -1060, -745, 140, 50, -4, -1).
%o A124948 (S/R) stvar $[N]:(0..M-1) init $[]:=0 asgn $[]->{*} kill +[i in 0..N-1](($[i]`-$[(i+1)mod N]`>2)+($[(i+1)mod N]`-$[i]`>2))
%Y A124948 Cf. Row 20 of A285280.
%K A124948 nonn,base
%O A124948 0,2
%A A124948 _R. H. Hardin_, Dec 28 2006