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 A157546 Half the number of length n integer sequences with sum zero and sum of squares 392. 1

%I

%S 1,9,54,1290,47385,1080891,19941831,335927439,5541820740,87714576070,

%T 1349748111657,20228679068676,290345411571852,3966279413712840,

%U 51810189395306490,652108043960695984,7955418278826810531

%N Half the number of length n integer sequences with sum zero and sum of squares 392.

%H R. H. Hardin, <a href="/A157546/b157546.txt">Table of n, a(n) for n=2..50</a>

%F [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,0,392)/2.

%K nonn

%O 2,2

%A _R. H. Hardin_ Mar 02 2009

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Last modified December 8 03:48 EST 2022. Contains 358672 sequences. (Running on oeis4.)