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 A224336 Number of idempotent 5X5 0..n matrices of rank 4. 1
 155, 805, 2555, 6245, 12955, 24005, 40955, 65605, 99995, 146405, 207355, 285605, 384155, 506245, 655355, 835205, 1049755, 1303205, 1599995, 1944805, 2342555, 2798405, 3317755, 3906245, 4569755, 5314405, 6146555, 7072805, 8099995, 9235205 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Row 5 of A224333. LINKS R. H. Hardin, Table of n, a(n) for n = 1..210 Index entries for linear recurrences with constant coefficients, signature (5,-10,10,-5,1). FORMULA a(n) = 10*n^4 + 40*n^3 + 60*n^2 + 40*n + 5. a(n) = 5*a(n-1) - 10*a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5). - Colin Barker, Sep 20 2014 G.f.: -5*x*(x^4-6*x^3+16*x^2+6*x+31) / (x-1)^5. - Colin Barker, Sep 20 2014 EXAMPLE Some solutions for n=3 ..1..0..0..1..0....0..0..0..0..0....0..2..3..2..2....1..0..0..1..0 ..0..1..0..1..0....1..1..0..0..0....0..1..0..0..0....0..1..0..2..0 ..0..0..1..2..0....3..0..1..0..0....0..0..1..0..0....0..0..1..2..0 ..0..0..0..0..0....2..0..0..1..0....0..0..0..1..0....0..0..0..0..0 ..0..0..0..2..1....3..0..0..0..1....0..0..0..0..1....0..0..0..1..1 PROG (PARI) Vec(-5*x*(x^4-6*x^3+16*x^2+6*x+31)/(x-1)^5 + O(x^100)) \\ Colin Barker, Sep 20 2014 CROSSREFS Sequence in context: A129640 A028382 A250936 * A218328 A101535 A010086 Adjacent sequences:  A224333 A224334 A224335 * A224337 A224338 A224339 KEYWORD nonn,easy AUTHOR R. H. Hardin, formula via M. F. Hasler William J. Keith and Rob Pratt in the Sequence Fans Mailing List, Apr 03 2013 STATUS approved

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Last modified June 15 15:16 EDT 2021. Contains 345049 sequences. (Running on oeis4.)