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A157560 Half the number of length n integer sequences with sum zero and sum of squares 1568. 1
1, 9, 54, 4730, 384345, 17551611, 639200583, 21540673143, 709364141280, 22449552443395, 690983408959437, 20713553342449344, 594627688939323130, 16245942354519666285, 424430686079103349170, 10684143371864906288080 (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,0,1568)/2.

CROSSREFS

Sequence in context: A157539 A205814 A157546 * A157588 A270575 A058849

Adjacent sequences:  A157557 A157558 A157559 * A157561 A157562 A157563

KEYWORD

nonn

AUTHOR

R. H. Hardin Mar 02 2009

STATUS

approved

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Last modified October 4 19:10 EDT 2022. Contains 357239 sequences. (Running on oeis4.)