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A224525 Number of idempotent 3 X 3 0..n matrices of rank 1. 2
27, 69, 123, 195, 273, 375, 477, 603, 735, 885, 1035, 1221, 1395, 1593, 1803, 2031, 2253, 2511, 2757, 3039, 3321, 3615, 3909, 4251, 4575, 4917, 5271, 5649, 6015, 6429, 6819, 7245, 7671, 8109, 8559, 9051, 9513, 9999, 10497, 11031, 11541, 12099, 12633 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Row 3 of A224524.
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000 (first 80 terms from R. H. Hardin)
FORMULA
a(n) = 6*n^2 + 18*n + 3 + 6 * A002541(n). - Robert Israel, Dec 15 2019
EXAMPLE
Some solutions for n=3:
0 1 0 1 3 2 0 1 0 1 3 1 0 0 0 0 0 0 1 0 0
0 1 0 0 0 0 0 1 0 0 0 0 0 1 2 3 0 3 1 0 0
0 3 0 0 0 0 0 2 0 0 0 0 0 0 0 1 0 1 2 0 0
MAPLE
f:= k -> 6*k^2 + 18*k + 3 + 6 * add(floor(k/m), m=2..k):
map(f, [$1..50]); # Robert Israel, Dec 15 2019
CROSSREFS
Sequence in context: A065008 A250134 A116353 * A219130 A116302 A181976
KEYWORD
nonn
AUTHOR
R. H. Hardin, Apr 09 2013
STATUS
approved

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Last modified April 22 10:51 EDT 2024. Contains 371897 sequences. (Running on oeis4.)