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A083531 First difference sequence of A002191. Differences between possible values for sum of divisors of n. 4
2, 1, 2, 1, 1, 4, 1, 1, 1, 3, 2, 4, 4, 2, 1, 1, 4, 2, 1, 1, 2, 2, 4, 6, 2, 1, 3, 2, 1, 5, 4, 2, 4, 2, 4, 6, 1, 2, 3, 2, 4, 2, 4, 2, 2, 2, 6, 1, 3, 2, 1, 1, 4, 1, 5, 2, 4, 6, 2, 4, 2, 2, 2, 2, 4, 3, 3, 2, 4, 2, 1, 3, 6, 2, 1, 3, 2, 4, 6, 2, 4, 1, 5, 2, 4, 2, 4, 6, 2, 6, 4, 3, 1, 2, 2, 4, 2, 4, 2, 6, 2, 2, 2, 4, 6 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..105.

EXAMPLE

8 and 12 are the 6th and 7th possible values for sigma[x], since they are sum of divisors of x=7 and x=11 respectively, while 9,10,11 are impossible ones so 12-8=4=a(6)= A002191(7)-A002191(6).

MATHEMATICA

t=Table[DivisorSigma[1, w], {w, 1, 25000}]; u=Union[%]; Delete[u-RotateRight[u], 1]

CROSSREFS

Cf. A002191, A007609, A007369, A083532-A083536.

Sequence in context: A134303 A078997 A024680 * A003417 A158986 A079900

Adjacent sequences:  A083528 A083529 A083530 * A083532 A083533 A083534

KEYWORD

nonn

AUTHOR

Labos Elemer, May 20 2003

STATUS

approved

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Last modified October 30 07:54 EDT 2014. Contains 248796 sequences.