A067479 Smallest n-digit square starting with 9, or 0 if no such number exists.

9, 0, 900, 9025, 90000, 900601, 9000000, 90003169, 900000000, 9000127161, 90000000000, 900001331856, 9000000000000, 90000000369889, 900000000000000, 9000000036988900, 90000000000000000, 900000001801523401

Offset: 1

Author

Amarnath Murthy, Feb 09 2002

Keywords

• base
• easy
• nonn

Crossrefs

Cf. A000290, A035076 (roots), A045792.

Cf. 2: A067472, 3: A067473, 4: A067474, 5: A067475, 6: A067476, 7: A067477, 8: A067478.

Programs

PARI

a(n) = if (n==2, 0, (sqrtint(9*10^(n-1)) + (n-1) % 2)^2); \\ Michel Marcus, Mar 23 2021

Formula

a(n+1) = (floor(sqrt(9*10^n)) + (n mod 2))^2, a(2)=0. - Sascha Kurz, Mar 18 2002

a(2k+1) = 9 * 10^(2k) for k >= 0. - Bernard Schott, Mar 23 2021

Extensions

More terms from Sascha Kurz, Mar 18 2002