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

Reinhard Zumkeller, Table of n, a(n) for n = 1..1000

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 A064895 A120877

Adjacent sequences:  A165927 A165928 A165929 * A165931 A165932 A165933

KEYWORD

nonn

AUTHOR

Jaroslav Krizek, Sep 30 2009

EXTENSIONS

Program and editing by Charles R Greathouse IV, Nov 02 2009

STATUS

approved

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Last modified August 24 02:32 EDT 2019. Contains 326260 sequences. (Running on oeis4.)