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A159367 Number of n X n arrays of squares of integers summing to 7 1
4, 540, 18720, 531300, 8583300, 86748088, 623757696, 3483871560, 16023245700, 63174296020, 219752181792, 688950636972, 1978607887620, 5271705817200, 13162584962560, 31050835145616, 69671782148868, 149524133455500 (list; graph; refs; listen; history; text; internal format)
OFFSET
2,1
COMMENTS
All such sequences have holonomic recurrences (cf. comment in A159359). - Georg Fischer, Feb 17 2022
LINKS
Index entries for linear recurrences with constant coefficients, signature (15, -105, 455, -1365, 3003, -5005, 6435, -6435, 5005, -3003, 1365, -455, 105, -15, 1).
FORMULA
Empirical: a(n)=n^2*(n-1)*(n+1)*(n^2-2)*(n^2-3)*(n^6-15*n^4+74*n^2+720)/5040. [From R. J. Mathar, Aug 11 2009]
CROSSREFS
Sequence in context: A152463 A295206 A209608 * A012770 A332154 A202032
KEYWORD
nonn
AUTHOR
R. H. Hardin Apr 11 2009
STATUS
approved

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Last modified June 22 04:48 EDT 2024. Contains 373565 sequences. (Running on oeis4.)