A396618 - OEIS

%I #14 Jun 10 2026 14:30:58

%S 4,3,4,8,26,70,206,674,2032,6431,20096,63708,200646,634782,2005025,

%T 6341137,20044802,63389326,200432444,633827657,2004269529

%N a(n) is the number of n-digit terms in A192689 with a(1) = 4.

%t A192689Q[k_]:=NoneTrue[Table[Mod[k, 10^d], {d, IntegerLength[k] - 1}], IntegerQ[Sqrt[#]] &]; a[n_]:=KroneckerDelta[n,1]+Length[Select[Range[Ceiling[Sqrt[10^(n - 1)]], Floor[Sqrt[10^n-1]]]^2, A192689Q]]; Array[a,12]

%Y Cf. A017934, A017936, A192689.

%K nonn,base,more

%O 1,1

%A _Stefano Spezia_, May 31 2026

%E a(18)-a(21) from _Michael S. Branicky_, Jun 10 2026