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A159395 Number of n X n arrays of squares of integers summing to 15. 1
12, 3480, 695776, 146278160, 24075289500, 2757589446360, 199926892967040, 9002136703356360, 266012140249399740, 5540786512741512384, 86568566944442320608, 1065719011381263788328, 10740917528961226530924 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,1

COMMENTS

There are either one 9, one 4 and two 1's, or one 9 and six 1's, or three 4's and three 1's, or two 4's and seven 1's, or one 4 and eleven 1's, or fifteen 1's, and in each case the rest are 0's. - Robert Israel, Jun 04 2020

LINKS

R. H. Hardin, Table of n, a(n) for n = 2..100

FORMULA

Empirical G.f.: -4*x^2*(1+x)*(3 + 774*x + 147595*x^2 + 31420746*x^3 +4930813594*x^4 + 514132877008*x^5 + 30735972011770*x^6 +965001688149346*x^7 + 16097428576776773*x^8 +150031357184487178*x^9 + 818650552471356653*x^10 +2702659491995569492*x^11 + 5503456361992829612*x^12 +6971617718513038912*x^13 + 5503456361992829612*x^14 +2702659491995569492*x^15 + 818650552471356653*x^16 +150031357184487178*x^17 + 16097428576776773*x^18 +965001688149346*x^19 + 30735972011770*x^20 + 514132877008*x^21 +4930813594*x^22 + 31420746*x^23 + 147595*x^24 + 774*x^25 + 3*x^26)/(-1+x)^31. - Vaclav Kotesovec, Nov 30 2012

From Robert Israel, Jun 04 2020: (Start) Empirical g.f. confirmed.

a(n) = (n^30 - 105*n^28 + 5005*n^26 - 110565*n^24 + 587587*n^22 + 25750725*n^20 - 572127985*n^18 + 4357458105*n^16 + 651498848*n^14 - 209929880160*n^12 + 1338174481280*n^10 - 3184977017040*n^8 + 1625807456064*n^6 + 3390523799040*n^4 - 2964061900800*n^2)/15!. (End)

MAPLE

seq((n^30 - 105*n^28 + 5005*n^26 - 110565*n^24 + 587587*n^22 + 25750725*n^20 - 572127985*n^18 + 4357458105*n^16 + 651498848*n^14 - 209929880160*n^12 + 1338174481280*n^10 - 3184977017040*n^8 + 1625807456064*n^6 + 3390523799040*n^4 - 2964061900800*n^2)/15!, n=2..30); # Robert Israel, Jun 04 2020

CROSSREFS

Sequence in context: A077749 A077297 A012609 * A272093 A099186 A307944

Adjacent sequences:  A159392 A159393 A159394 * A159396 A159397 A159398

KEYWORD

nonn,easy

AUTHOR

R. H. Hardin, Apr 11 2009

STATUS

approved

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Last modified April 20 15:04 EDT 2021. Contains 343135 sequences. (Running on oeis4.)