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A278933
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Number of 2 X 2 matrices with entries in {0,1,...,n} and permanent = trace with no entry repeated.
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2
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0, 0, 0, 0, 0, 0, 4, 4, 8, 8, 12, 12, 20, 20, 24, 28, 32, 32, 40, 40, 48, 52, 56, 56, 68, 68, 72, 76, 84, 84, 96, 96, 104, 108, 112, 116, 128, 128, 132, 136, 148, 148, 160, 160, 168, 176, 180, 180, 196, 196, 204
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OFFSET
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0,7
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COMMENTS
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a(n) mod 4 = 0.
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LINKS
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PROG
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(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, 286):
print str(i)+" "+str(t(i))
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CROSSREFS
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Cf. A210288 (wherein the entries can be repeated).
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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