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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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified October 17 10:50 EDT 2017. Contains 293469 sequences.