



1, 3, 5, 8, 15, 9, 20, 40, 27, 13, 21, 45, 39, 63, 48, 72, 100, 21, 135, 25, 65, 104, 63, 168, 33, 180, 81, 75, 195, 112, 240, 65, 37, 360, 105, 117, 189, 168, 99, 45, 243, 260, 125, 420, 195, 111, 200, 520, 315, 351, 567, 273, 57, 432, 135, 61, 165, 256, 900, 189, 375
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OFFSET

1,2


COMMENTS

A permutation of sequence A018804, which gives the sum of gcd (k,n) for 1 <= k <= n.


LINKS



FORMULA

The multiplicative formula for the numerator in a positive integer's centrality fraction is: for prime p, a(p^e)= p^(e1)*((p1)e+p) (cf. A018804). Dividing by the square of the integer gives the integer's centrality, which is defined to be the average fraction of the integer that it shares with the other integers as a gcd; see A080997 for other interpretations. This sequence gives the unreduced centrality numerators for A080997(n), where A080997 is the sequence of positive integers in nonincreasing order of their centrality.


CROSSREFS

Cf. A080997, A080998 for centrality rankings of the positive integers.


KEYWORD

nonn


AUTHOR



STATUS

approved



