A355574 - OEIS

A355574

Number of nonnegative integers k with n digits such that x^2 - s*x + p has only integer roots, where s and p denote the sum and product of the digits of k respectively.

%I #17 Jul 14 2022 09:34:30

%S 2,90,223,2686,31601,370894,4220160,46962379,512600193

%N Number of nonnegative integers k with n digits such that x^2 - s*x + p has only integer roots, where s and p denote the sum and product of the digits of k respectively.

%C a(n) is the number of n-digit numbers in A355497.

%F a(n) <= A063945(n).

%F Limit_{n->infinity} a(n)/a(n-1) = 10.

%Y Cf. A355497.

%Y Cf. A007953, A007954, A063945, A355547.

%K nonn,base,hard,more

%O 1,1

%A _Stefano Spezia_, Jul 07 2022

%E a(8)-a(9) from _Jean-Marc Rebert_, Jul 13 2022