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.

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

Offset

1,1

Comments

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

Links

Table of n, a(n) for n=1..9.

Formula

a(n) <= A063945(n).

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

Crossrefs

Cf. A355497.

Cf. A007953, A007954, A063945, A355547.

Sequence in context: A339581 A256962 A266807 * A076532 A212301 A226339

Adjacent sequences: A355571 A355572 A355573 * A355575 A355576 A355577

Keyword

nonn,base,hard,more

Author

Stefano Spezia, Jul 07 2022

Extensions

a(8)-a(9) from Jean-Marc Rebert, Jul 13 2022

Status

approved