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A165930
a(1) = 1, for n > 1: a(n) = tau(sum of the previous terms) where tau(k) = number of the divisors of k.
2
1, 1, 2, 3, 2, 3, 6, 6, 8, 6, 4, 8, 6, 8, 7, 2, 2, 6, 5, 4, 12, 8, 8, 4, 4, 12, 8, 4, 12, 10, 6, 4, 8, 8, 12, 16, 4, 8, 8, 8, 4, 8, 8, 4, 4, 8, 8, 4, 4, 12, 8, 4, 16, 4, 12, 4, 8, 8, 4, 4, 16, 8, 12, 8, 8, 8, 18, 18, 12, 8, 8, 4, 8, 4, 8, 4, 4, 16, 4, 4, 16, 4, 8, 8, 8, 4, 8, 4, 24, 8, 4, 12, 8, 8, 4, 4, 16
OFFSET
1,3
COMMENTS
a(1) = 1, for n > 1: a(n) = tau(sum_(i=1...n-1) a(i)) = A000005(sum_(i=1...n-1) a(i)). a(n) = inverse of partial sums of A064491(n), i.e. a(1) = A064491(1), for n > 1: a(n) = A064491(n) - A064491(n-1), i.e. first differences of sequence A064491.
LINKS
EXAMPLE
a(4) = tau(a(1)+a(2)+a(3)) = tau(4) = 3.
PROG
(PARI) print1(1); s=1; for(n=2, 1e4, a=numdiv(s); print1(", "a); s+=a)
(Haskell)
a165930 n = a165930_list !! (n-1)
a165930_list = 1 : zipWith (-) (tail a064491_list) a064491_list
-- Reinhard Zumkeller, Mar 29 2014
CROSSREFS
Sequence in context: A085211 A085212 A079025 * A300500 A339132 A064895
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, Sep 30 2009
EXTENSIONS
Program and editing by Charles R Greathouse IV, Nov 02 2009
STATUS
approved