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A239277
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Smallest start for n consecutive numbers such that the product of any two numbers is unique.
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3
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1, 1, 1, 2, 3, 5, 5, 7, 11, 13, 13, 22, 22, 26, 33, 37, 37, 51, 51, 57, 67, 73, 73, 92, 92, 113, 113, 122, 145, 145, 145, 172, 183, 211, 211, 211, 243, 261, 281, 290, 295, 326, 331, 346, 369, 385, 385, 426, 426, 443, 469, 487, 487, 533, 533, 581, 581, 601, 601
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OFFSET
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1,4
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COMMENTS
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a(n-1) <= a(n) <= n^2.
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LINKS
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EXAMPLE
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For n=4 we have a(n)=2; 1 is impossible because 1*4=2*2; on the other hand the products of any two numbers from 2,3,4,5 are 4,6,8,9,10,12,15,16,20,25, which are all distinct.
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PROG
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(Sage)
def find_start(n):
q=1
while True:
L={}
advance=True
for i in range(n-1):
for j in range(i, n):
if (q+i)*(q+j) not in L:
L[(q+i)*(q+j)]=1
else:
advance=False
break
if not advance:
break
else:
return q
q+=1
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CROSSREFS
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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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