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A053807 Sum_{k=1..n, n mod k = 1} k^2. 3
0, 0, 4, 9, 20, 25, 49, 49, 84, 90, 129, 121, 209, 169, 249, 259, 340, 289, 454, 361, 545, 499, 609, 529, 849, 650, 849, 819, 1049, 841, 1299, 961, 1364, 1219, 1449, 1299, 1910, 1369, 1809, 1699, 2209, 1681, 2499, 1849, 2561, 2365, 2649 (list; graph; refs; listen; history; internal format)
OFFSET

1,3

FORMULA

a(n) = sigma_2(n-1) - 1.

CROSSREFS

Cf. A001157.

Sequence in context: A136769 A115075 A063454 * A066109 A030734 A073360

Adjacent sequences:  A053804 A053805 A053806 * A053808 A053809 A053810

KEYWORD

nonn

AUTHOR

N. J. A. Sloane (njas(AT)research.att.com), Apr 07 2000

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Last modified February 14 06:58 EST 2012. Contains 205577 sequences.