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A074927
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a(n) such that p(n)*p(n+1)+a(n) is a minimal square.
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5
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3, 1, 1, 4, 1, 4, 1, 4, 9, 1, 9, 4, 1, 4, 9, 9, 1, 9, 4, 1, 9, 4, 9, 16, 4, 1, 4, 1, 4, 49, 4, 9, 1, 25, 1, 9, 9, 4, 9, 9, 1, 25, 1, 4, 1, 36, 36, 4, 1, 4, 9, 1, 25, 9, 9, 9, 1, 9, 4, 1, 25, 49, 4, 1, 4, 49, 9, 25, 1, 4, 9, 16, 9, 9, 4, 9, 16, 4, 16, 25, 1, 25, 1, 9, 4, 9, 16, 4, 1, 4, 36, 16, 4
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OFFSET
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1,1
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COMMENTS
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When a(n)=1, p(n) and p(n+1) are twin primes.
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LINKS
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FORMULA
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EXAMPLE
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a(154) = 100 because p(154)*p(155) + 100 = 804609 = 897^2.
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MATHEMATICA
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Flatten[{3, Table[((Prime[n+1]-Prime[n])/2)^2, {n, 2, 100}]}] (* Vaclav Kotesovec, Mar 23 2014 *)
Join[{3}, ((#[[2]]-#[[1]])/2)^2&/@Partition[Prime[Range[2, 100]], 2, 1]] (* Harvey P. Dale, Dec 04 2016 *)
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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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