login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A318593 Number of n-member subsets of [5*n] whose elements sum to a multiple of five. 2
1, 1, 9, 91, 969, 10630, 118755, 1344904, 15380937, 177232627, 2054455670, 23930713170, 279871768995, 3284214703056, 38650751381832, 456002537343580, 5391644226101705, 63871405575418665, 757929628541719755, 9007607943130625829, 107196674080761940470 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..922

FORMULA

a(n) = floor(A163456(n)) + [n mod 5 = 0]*A163455(n/5), with A163456(n) = binomial(5*n,n)/5 and A163455(n) = binomial(5*n-1,n) where [] is an Iverson bracket. - Georg Fischer, Mar 23 2019

EXAMPLE

a(2) = 9: {1,4}, {1,9}, {2,3}, {2,8}, {3,7}, {4,6}, {5,10}, {6,9}, {7,8}.

MAPLE

b:= proc(n, s, m, t) option remember; `if`(n=0, `if`(s=0 and t=0, 1, 0),

      b(n-1, s, m, t)+`if`(t=0, 0, b(n-1, irem(s+n, m), m, t-1)))

    end:

a:= n-> b(5*n, 0, 5, n):

seq(a(n), n=0..27);

CROSSREFS

Column k=5 of A318557.

Cf. A163455, A163456.

Sequence in context: A242299 A109108 A163456 * A176735 A286786 A123792

Adjacent sequences:  A318590 A318591 A318592 * A318594 A318595 A318596

KEYWORD

nonn

AUTHOR

Alois P. Heinz, Aug 29 2018

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 May 24 16:47 EDT 2019. Contains 323533 sequences. (Running on oeis4.)