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A335708
a(n) is the number of divisors of the n-th Niven number.
1
1, 2, 2, 3, 2, 4, 2, 4, 3, 4, 6, 6, 6, 4, 8, 4, 8, 9, 8, 8, 6, 10, 6, 8, 12, 6, 8, 12, 10, 5, 12, 12, 9, 8, 12, 8, 4, 10, 8, 6, 16, 12, 12, 4, 8, 12, 15, 12, 8, 6, 12, 10, 6, 18, 8, 14, 8, 12, 12, 4, 12, 6, 4, 16, 16, 12, 8, 12, 9, 12, 8, 12, 20, 6, 4, 18, 6, 16
OFFSET
1,2
FORMULA
a(n) = A000005(A005349(n)).
EXAMPLE
The first Niven number is 1 and tau(1) = 1, so a(1) = 1.
The second Niven number is 2 and tau(2) = 2, so a(2) = 2.
The 11th Niven number is 12 and tau(12) = 6, so a(11) = 6.
MATHEMATICA
DivisorSigma[0, Select[Range[265], Divisible[#, Plus @@ IntegerDigits[#]] &]] (* Amiram Eldar, Aug 04 2020 *)
PROG
(Magma) niven:=func<n|n mod &+Intseq(n) eq 0 >; [#Divisors(k):k in [1..300]|niven(k)];
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Marius A. Burtea, Aug 04 2020
STATUS
approved