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A116086
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Perfect powers n with no primes between n and the next larger perfect power, which is in A116455.
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1
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OFFSET
| 1,1
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COMMENTS
| No other n<10^12. There is a conjecture that this sequence is finite.
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LINKS
| March 2006 NMBRTHRY Archives
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EXAMPLE
| The prime-free ranges are (2^3,3^2), (5^2,3^3), (2^5,6^2), (11^2,5^3), (3^7,13^3), (5^5,56^2), (181^2,2^15), (43^3,282^2), (46^3,312^2), (22434^2,55^5).
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MATHEMATICA
| lim=10^12; lst={}; k=2; While[n=Floor[lim^(1/k)]; n>=2, lst=Join[lst, Range[2, n]^k]; k++ ]; lst=Union[lst]; PrimeFree[n1_, n2_] := Module[{n=n1+1}, While[n<n2&&!PrimeQ[n], n++ ]; n ==n2]; lst2={}; Do[If[PrimeFree[lst[[i]], lst[[i+1]]], AppendTo[lst2, lst[[i]]]], {i, Length[lst]-1}]; lst2
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CROSSREFS
| Cf. A001597 (perfect powers).
Sequence in context: A045860 A081504 A030796 * A042611 A160758 A015804
Adjacent sequences: A116083 A116084 A116085 * A116087 A116088 A116089
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KEYWORD
| hard,nonn
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AUTHOR
| T. D. Noe (noe(AT)sspectra.com), Mar 28 2006
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