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A111150 a(n) is the number of integers of the form (n+k)/|(n-k)| for k>0. 3
2, 4, 6, 6, 6, 10, 6, 8, 10, 10, 6, 14, 6, 10, 14, 10, 6, 16, 6, 14, 14, 10, 6, 18, 10, 10, 14, 14, 6, 22, 6, 12, 14, 10, 14, 22, 6, 10, 14, 18, 6, 22, 6, 14, 22, 10, 6, 22, 10, 16, 14, 14, 6, 22, 14, 18, 14, 10, 6, 30, 6, 10, 22, 14, 14, 22, 6, 14, 14, 22, 6, 28, 6, 10, 22, 14, 14, 22 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(n) <= 2^(n-1) and a(p)=6 for odd primes. - Robert G. Wilson v

LINKS

Ivan Neretin, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = 2*tau(2n) - 2, tau = A000005. - Ivan Neretin, Sep 07 2017

EXAMPLE

For n=7 we have integer value for the form when k={5; 6; 8; 9; 14; 21} and (7+k)/|(7-k)| = {6, 13, 15, 8, 3, 2}. Thus a(7) = 6.

MATHEMATICA

f[n_] := Length[ Select[(n + #)/Abs[n - # ] & /@ Delete[ Range[ Floor[5n/3]], n], IntegerQ[ # ] &]] + 2; Array[f, 78] (* Robert G. Wilson v *)

Table[2 DivisorSigma[0, 2 n] - 2, {n, 78}] (* Ivan Neretin, Sep 07 2017 *)

CROSSREFS

Cf. A000005.

Sequence in context: A207540 A050825 A174342 * A166983 A078611 A211376

Adjacent sequences:  A111147 A111148 A111149 * A111151 A111152 A111153

KEYWORD

easy,nonn

AUTHOR

Paolo P. Lava & Giorgio Balzarotti, Oct 19 2005

EXTENSIONS

Edited and extended by Robert G. Wilson v, Oct 19 2005

STATUS

approved

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Last modified April 7 12:45 EDT 2020. Contains 333305 sequences. (Running on oeis4.)