The On-Line Encyclopedia of Integer Sequences (OEIS)

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A157547

Half the number of length n integer sequences with sum zero and sum of squares 450.
(history; published version)

#4 by Russ Cox at Sat Mar 31 12:35:25 EDT 2012

AUTHOR

_R. H. Hardin (rhhardin(AT)att.net) _ Mar 02 2009

Discussion

Sat Mar 31

12:35

OEIS Server: https://oeis.org/edit/global/875

#3 by N. J. A. Sloane at Thu Nov 11 07:34:06 EST 2010

LINKS

R. H. Hardin, <a href="/A157547/b157547.txt">Table of n, a(n) for n=2..50</a>

KEYWORD

nonn,new

nonn

#2 by N. J. A. Sloane at Sat Oct 02 03:00:00 EDT 2010

LINKS

Ron R. H. Hardin, <a href="b157547.txt">Table of n, a(n) for n=2..50</a>

KEYWORD

nonn,new

nonn

AUTHOR

Ron R. H. Hardin (rhhardin(AT)att.net) Mar 02 2009

#1 by N. J. A. Sloane at Tue Jun 01 03:00:00 EDT 2010

NAME

Half the number of length n integer sequences with sum zero and sum of squares 450.

DATA

1, 3, 126, 2170, 37335, 921333, 21967484, 466292604, 9161931075, 164162481681, 2705726857350, 41747317681290, 619096670144225, 8923605271290360, 124998845674120920, 1699006653803990456, 22382667992161145863

OFFSET

2,2

LINKS

Ron Hardin, <a href="b157547.txt">Table of n, a(n) for n=2..50</a>

FORMULA

[cache enabling] count(n,s,ss)->count(n,t,tt) where t=s mod n, q=(t-s)/n, tt=ss+2*q*s+n*q^2; count(n,t,tt)=sum[i^2<=tt]{ count(n-1,t-i,tt-i^2) }. a(n)=count(n,0,450)/2.

KEYWORD

nonn

AUTHOR

Ron Hardin (rhhardin(AT)att.net) Mar 02 2009

STATUS

approved