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A157538 Half the number of length n integer sequences with sum zero and sum of squares 72. 1
1, 3, 18, 210, 2565, 32193, 299299, 2161092, 14903940, 101124595, 666560697, 4246100664, 25977358680, 152079371640, 852145833870, 4596664464916, 24033240110143, 122242188808411, 605721155611160, 2925464857935060 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,2

LINKS

R. H. Hardin, Table of n, a(n) for n=2..50

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,0,72)/2.

CROSSREFS

Sequence in context: A330764 A277355 A135077 * A024488 A217902 A183241

Adjacent sequences:  A157535 A157536 A157537 * A157539 A157540 A157541

KEYWORD

nonn

AUTHOR

R. H. Hardin Mar 02 2009

STATUS

approved

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Last modified August 12 22:46 EDT 2022. Contains 356077 sequences. (Running on oeis4.)