login
A067479
Smallest n-digit square starting with 9, or 0 if no such number exists.
8
9, 0, 900, 9025, 90000, 900601, 9000000, 90003169, 900000000, 9000127161, 90000000000, 900001331856, 9000000000000, 90000000369889, 900000000000000, 9000000036988900, 90000000000000000, 900000001801523401
OFFSET
1,1
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
KEYWORD
base,easy,nonn
AUTHOR
Amarnath Murthy, Feb 09 2002
EXTENSIONS
More terms from Sascha Kurz, Mar 18 2002
STATUS
approved