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A035071
a(n) = ceiling(sqrt(4*10^n)).
2
2, 7, 20, 64, 200, 633, 2000, 6325, 20000, 63246, 200000, 632456, 2000000, 6324556, 20000000, 63245554, 200000000, 632455533, 2000000000, 6324555321, 20000000000, 63245553204, 200000000000, 632455532034, 2000000000000
OFFSET
0,1
COMMENTS
Previous name: "a(n) is root of square starting with digit 4: first term of runs."
MATHEMATICA
Table[Ceiling @ Sqrt[4 * 10^n], {n, 0, 24}] (* Amiram Eldar, Oct 08 2019 *)
CROSSREFS
Cf. A067474 (squares), A035076 (2..9).
Sequence in context: A216246 A322202 A000935 * A055891 A122877 A192680
KEYWORD
nonn,base
AUTHOR
Patrick De Geest, Nov 15 1998
STATUS
approved