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A111715 Sum of the squares of the first n squarefree numbers. 3
0, 1, 5, 14, 39, 75, 124, 224, 345, 514, 710, 935, 1224, 1585, 2026, 2510, 3039, 3715, 4556, 5456, 6417, 7506, 8662, 9887, 11256, 12700, 14221, 15902, 17666, 19515, 21631, 23840, 26441, 29250, 32275, 35524, 38888, 42369, 46090, 49934, 54159 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

a(n) is prime for a(2) = 5, a(23) = 9887, a(26) = 14221, ... a(n) is semiprime for n = 3, 4, 9, 13, 14, 16, 17, 27, 30, 32, 39, 43, 44, 46, 47, ...

LINKS

Table of n, a(n) for n=0..40.

Eric Weisstein's World of Mathematics, Squarefree.

FORMULA

a(n) = A005117(1)^2 + ... A005117(n)^2.

EXAMPLE

a(10) = 1^2 + 2^2 + 3^2 + 5^2 + 6^2 + 7^2 + 10^2 + 11^2 + 13^2 + 14^2 = 710.

MATHEMATICA

Join[{0}, Accumulate[Select[Range[100], SquareFreeQ]^2]] (* Harvey P. Dale, Apr 08 2015 *)

CROSSREFS

Cf. A005117.

Sequence in context: A183898 A225865 A319648 * A024525 A209536 A119996

Adjacent sequences:  A111712 A111713 A111714 * A111716 A111717 A111718

KEYWORD

nonn

AUTHOR

Jonathan Vos Post, Nov 17 2005

STATUS

approved

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Last modified March 23 05:36 EDT 2019. Contains 321422 sequences. (Running on oeis4.)