login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A138707 Number of divisors of n that are also divisors of some d(k)*10^k, where n=Sum(d(k)*10^k). 4

%I #4 Mar 30 2012 18:50:59

%S 1,2,2,3,2,4,2,4,3,4,1,2,1,2,2,2,1,2,1,6,1,2,1,3,2,2,1,3,1,8,1,2,2,2,

%T 2,4,1,2,2,8,1,2,1,3,2,2,1,4,1,6,1,2,1,2,2,2,1,2,1,12,1,2,2,3,2,4,1,3,

%U 2,8,1,2,1,2,2,2,2,2,1,10,1,2,1,3,2,2,1,4,1,12,1,2,2,2,2,4,1,2,3,9,1,2,1,3

%N Number of divisors of n that are also divisors of some d(k)*10^k, where n=Sum(d(k)*10^k).

%C a(A138708(n)) = 1; a(A037124(n)) = A000005(A037124(n)).

%H R. Zumkeller, <a href="/A138707/b138707.txt">Table of n, a(n) for n = 1..10000</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/DivisorFunction.html">Divisor Function</a>

%e n = 216 = 2*10^2 + 1*10^1 + 6*10^0: let D(n) = set of divisors of

%e n,

%e D(216)={1,2,3,4,6,8,9,12,18,24,27,36,54,72,108,216},

%e D(200)={1,2,4,5,8,10,20,25,40,50,100,200}, D(10)={1,2,5,10}, D(6)={1,2,3,6},

%e a(216) = #{1,2,3,4,6,8} = 6.

%Y Cf. A061116.

%K nonn,base

%O 1,2

%A _Reinhard Zumkeller_, Mar 26 2008

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified April 23 23:26 EDT 2024. Contains 371917 sequences. (Running on oeis4.)