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 A278902 Number of 2 X 2 matrices with entries in {0,1,...,n} with determinant = trace and no entry repeated. 2
 0, 0, 0, 0, 0, 8, 12, 24, 28, 40, 48, 68, 72, 100, 120, 132, 144, 188, 208, 252, 280, 304, 336, 396, 416, 464, 512, 556, 592, 668, 704, 776, 844, 900, 960, 1020, 1056, 1148, 1240, 1308, 1348, 1456, 1524, 1628, 1728, 1792, 1872, 2004, 2080, 2188, 2292 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,6 COMMENTS a(n) mod 4=0. LINKS Indranil Ghosh and Chai Wah Wu, Table of n, a(n) for n = 0..10000 (terms for n = 0..240 from Indranil Ghosh) PROG (Python) def t(n):     s=0     for a in range(0, n+1):         for b in range(0, n+1):             for c in range(0, n+1):                 for d in range(0, n+1):                     if (a!=b  and a!=d and b!=d and c!=a and c!=b and c!=d):                         if (a*d-b*c)==a+d:                             s+=1     return s for i in range(0, 241):     print str(i)+" "+str(t(i)) CROSSREFS Cf. A210286 (wherein the entries can be repeated). Sequence in context: A105571 A141616 A326994 * A088525 A054735 A162691 Adjacent sequences:  A278899 A278900 A278901 * A278903 A278904 A278905 KEYWORD nonn AUTHOR Indranil Ghosh, Nov 30 2016 STATUS approved

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Last modified December 10 04:15 EST 2019. Contains 329885 sequences. (Running on oeis4.)