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 A218209 #11 Jun 02 2025 08:10:11
%S A218209 2,1,3,4,12,31,86,230,681,1934,5634,15772
%N A218209 Number of n-digit primes that are of the form (k-2)^2 + (k-1)^2 + k^2.
%F A218209 a(n) = A218210(n) - A218210(n-1)
%t A218209 n = -1; Table[cnt = 0; While[n++; p = 3*n^2 + 2; p < 10^e, If[PrimeQ[p], cnt++]]; n--; cnt, {e, 10}] (* _T. D. Noe_, Oct 23 2012 *)
%t A218209 Table[Count[Table[Total[Range[n,n+2]^2],{n,-1,600000}],_?(PrimeQ[#] && IntegerLength[#]==k&)],{k,12}] (* _Harvey P. Dale_, Oct 17 2016 *)
%Y A218209 Cf. A027863, A027864, A218207, A218210, A218211.
%K A218209 nonn,base
%O A218209 1,1
%A A218209 _Martin Renner_, Oct 23 2012