

A335708


a(n) is the number of divisors of the nth 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
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OFFSET

1,2


LINKS

Table of n, a(n) for n=1..78.


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<nn mod &+Intseq(n) eq 0 >; [#Divisors(k):k in [1..300]niven(k)];


CROSSREFS

Cf. A000005, A005349, A007953.
Sequence in context: A218704 A144373 A086292 * A076640 A326198 A324105
Adjacent sequences: A335705 A335706 A335707 * A335709 A335710 A335711


KEYWORD

nonn,base


AUTHOR

Marius A. Burtea, Aug 04 2020


STATUS

approved



