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

1,1

Links

Table of n, a(n) for n=1..18.

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

Prog

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

Crossrefs

Cf. A000290, A035076 (roots), A045792.

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

Sequence in context: A177145 A178912 A191564 * A308803 A249489 A166734

Adjacent sequences: A067476 A067477 A067478 * A067480 A067481 A067482

Keyword

base,easy,nonn

Author

Amarnath Murthy, Feb 09 2002

Extensions

More terms from Sascha Kurz, Mar 18 2002

Status

approved