login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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 (list; graph; refs; listen; history; text; internal format)
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<n|n 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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified August 4 09:11 EDT 2021. Contains 346445 sequences. (Running on oeis4.)