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!)
A309189 (1/10) times the number of n-member subsets of [10n] whose elements sum to a multiple of n. 2
1, 9, 136, 2289, 42376, 834336, 17125354, 362345361, 7847250409, 173103073384, 3875837737520, 87857163416064, 2012268157890524, 46497242493163450, 1082614775186919136, 25374686712458407441, 598217593341171422090, 14176230568946364963825 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Also (1/9) times the number of n-member subsets of [10n-1] whose elements sum to a multiple of n.

LINKS

Alois P. Heinz, Table of n, a(n) for n = 1..712

FORMULA

a(n) = 1/(10n) * Sum_{d|n} binomial(10d,d)*(-1)^(n+d)*phi(n/d).

MAPLE

with(numtheory):

a:= n-> add(binomial(10*d, d)*(-1)^(n+d)*

        phi(n/d), d in divisors(n))/(10*n):

seq(a(n), n=1..25);

PROG

(PARI) a(n) = 1/(10*n) * sumdiv(n, d, binomial(10*d, d)*(-1)^(n+d)*eulerphi(n/d)); \\ Michel Marcus, Jul 20 2019

CROSSREFS

Column k=10 of A309148.

Sequence in context: A052137 A003376 A253879 * A231757 A156975 A081876

Adjacent sequences:  A309186 A309187 A309188 * A309190 A309191 A309192

KEYWORD

nonn

AUTHOR

Alois P. Heinz, Jul 15 2019

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 March 7 14:00 EST 2021. Contains 341886 sequences. (Running on oeis4.)