

A187209


Sum of all terms of triangle of absolute differences of the divisors of n.


2



0, 1, 2, 4, 4, 9, 6, 11, 12, 13, 10, 24, 12, 21, 30, 26, 16, 43, 18, 40, 40, 37, 22, 59, 40, 45, 50, 52, 28, 89, 30, 57, 60, 61, 86, 90, 36, 69, 70, 103, 40, 125, 42, 88, 140, 85, 46, 128, 84, 97, 90, 106, 52, 165, 130, 113, 100, 109, 58, 201
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OFFSET

1,3


COMMENTS

Note that if n is prime then a(n) = n  1.


LINKS

Table of n, a(n) for n=1..60.


FORMULA

a(n) = A187215(n)  A000203(n).


EXAMPLE

a(10) = 13 because the divisors of 10 are 1, 2, 5, 10; the triangle of absolute differences is
1, 3, 5;
. 2, 2;
. 0;
and the sum of the terms of triangle is 1+3+5+2+2+0 = 13.


MATHEMATICA

Table[Total[Flatten[NestList[Abs[Differences[#]]&, Differences[Divisors[ n]], DivisorSigma[0, n]1]]], {n, 60}] (* Harvey P. Dale, Aug 10 2011 *)


CROSSREFS

Cf. A187203, A187205, A187207, A187208.
Sequence in context: A201777 A096189 A010464 * A006579 A227906 A195727
Adjacent sequences: A187206 A187207 A187208 * A187210 A187211 A187212


KEYWORD

nonn


AUTHOR

Omar E. Pol, Aug 04 2011


STATUS

approved



