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
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