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A089887 Number of subsets of {1,.., n} containing no squares. 4
1, 2, 4, 4, 8, 16, 32, 64, 64, 128, 256, 512, 1024, 2048, 4096, 4096, 8192, 16384, 32768, 65536, 131072, 262144, 524288, 1048576, 1048576, 2097152, 4194304, 8388608, 16777216, 33554432, 67108864, 134217728, 268435456 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(n) = Product(2-A010052(k): 1<=k<=n) = A089886(n,0) = A000079(n)-A089888(n).

LINKS

Table of n, a(n) for n=1..33.

Index to divisibility sequences

FORMULA

a(n) = 2^(n-n^(1/2)).

PROG

(PARI) a(n)=2^(n-sqrtint(n)) \\ Charles R Greathouse IV, Apr 09 2012

CROSSREFS

Cf. A089889, A089890.

Sequence in context: A181217 A223569 A227594 * A161816 A240347 A160124

Adjacent sequences:  A089884 A089885 A089886 * A089888 A089889 A089890

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Nov 13 2003

STATUS

approved

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Last modified December 10 21:23 EST 2016. Contains 279011 sequences.