A216657 Number of n-digit 7th powers.

2, 0, 1, 1, 2, 2, 2, 4, 6, 7, 11, 14, 20, 28, 39, 55, 75, 104, 145, 202, 280, 390, 541, 752, 1045, 1452, 2017, 2803, 3895, 5412, 7520, 10449, 14519, 20174, 28031, 38950, 54120, 75200, 104490, 145188, 201738, 280314, 389496, 541202, 751998, 1044898, 1451881

Offset

1,1

Links

Alois P. Heinz, Table of n, a(n) for n = 1..1000

Example

a(1) = 2: 0, 1.
a(3) = 1: 128.
a(4) = 1: 2187.
a(5) = 2: 16384, 78125.
a(6) = 2: 279936, 823543.
a(7) = 2: 2097152, 4782969.
a(8) = 4: 10000000, 19487171, 35831808, 62748517.
a(9) = 6: 105413504, 170859375, 268435456, 410338673, 612220032, 893871739.

Maple

r:= proc(n, k) local b; b:= iroot(n, k); b+`if`(b^k<n, 1, 0) end:
a:= n-> r(10^n, 7) -r(10^(n-1), 7) +`if`(n=1, 1, 0):
seq(a(n), n=1..50);

Crossrefs

Column k=7 of A216653.

Sequence in context: A353945 A089614 A064875 * A328614 A257511 A039802

Adjacent sequences: A216654 A216655 A216656 * A216658 A216659 A216660

Keyword

nonn,base

Author

Alois P. Heinz, Sep 12 2012

Status

approved