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A157546 Half the number of length n integer sequences with sum zero and sum of squares 392. 1
1, 9, 54, 1290, 47385, 1080891, 19941831, 335927439, 5541820740, 87714576070, 1349748111657, 20228679068676, 290345411571852, 3966279413712840, 51810189395306490, 652108043960695984, 7955418278826810531 (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,0,392)/2.

CROSSREFS

Sequence in context: A093847 A157539 A205814 * A157560 A157588 A270575

Adjacent sequences:  A157543 A157544 A157545 * A157547 A157548 A157549

KEYWORD

nonn

AUTHOR

R. H. Hardin Mar 02 2009

STATUS

approved

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Last modified September 26 23:44 EDT 2022. Contains 357051 sequences. (Running on oeis4.)