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A076957
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Smallest k such that there are exactly n primes strictly between k^2 and (k+1)^2.
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4
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1, 4, 6, 10, 15, 16, 25, 24, 31, 39, 38, 45, 64, 48, 52, 57, 75, 82, 81, 70, 76, 79, 106, 112, 145, 111, 121, 117, 123, 134, 144, 139, 146, 154, 163, 192, 169, 176, 179, 193, 202, 218, 204, 226, 223, 240, 233, 238, 243, 259, 291, 256, 286, 309, 278
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OFFSET
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2,2
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COMMENTS
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Conjecturally, a(n) is undefined for n = 1 and defined for all n >= 2. (End)
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LINKS
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MAPLE
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a := proc(n) local k, h, SEARCHLIMIT; SEARCHLIMIT := 10000; h := proc(k) option remember; nops(select(j->isprime(j), [$k^2+1..(k+1)^2])) end: k := 1; while h(k) <> n and k < SEARCHLIMIT do k := k+1 od; `if`(k=SEARCHLIMIT, print("Search limit reached!"), k) end: seq(a(n), n=2..56); # Peter Luschny, Jan 10 2017
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MATHEMATICA
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Table[k = 1; While[Count[Map[PrimeQ, Range[k^2 + 1, (k + 1)^2]], True] != n, k++]; k, {n, 2, 56}] (* Michael De Vlieger, Jan 10 2017 *)
With[{pp=Table[Count[Range[n^2+1, (n+1)^2-1], _?(PrimeQ[#]&)], {n, 500}]}, Table[ Position[pp, k, 1, 1], {k, 60}]]//Flatten (* Harvey P. Dale, Aug 01 2021 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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