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A071220
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Numbers n such that prime(n) + prime(n+1) is a cube.
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3
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2, 28, 1332, 3928, 16886, 157576, 192181, 369440, 378904, 438814, 504718, 539873, 847252, 1291597, 1708511, 1837979, 3416685, 3914319, 5739049, 6021420, 7370101, 7634355, 8608315, 9660008, 10378270, 14797144, 15423070, 18450693
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Prime(n)+ Prime(n+1) is a square in A064397; n^2 is a sum of two successive primes in A074924; n^3 is a sum of two successive primes in A074925.
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FORMULA
| A001043(x)=m^3 for some m; if p(x+1)+p(x) is a cube, then x is here.
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EXAMPLE
| 28 is in the list because p(28)+p(29)=107+109=216=6^3.
n=1291597: p(1291597)+p(1291598)=344.344.344
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MATHEMATICA
| PrevPrim[n_] := Block[{k = n - 1}, While[ !PrimeQ[k], k-- ]; k]; NextPrim[n_] := Block[{k = n + 1}, While[ !PrimeQ[k], k++ ]; k]; Do[ If[ n^3 == PrevPrim[Floor[(n^3)/2]] + NextPrim[Floor[(n^3)/2]], Print[ PrimePi[ Floor[(n^3)/2]]]], {n, 2, 10^4}]
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CROSSREFS
| Cf. A064397, A074925, A074924, A001043.
Sequence in context: A186491 A009674 A143598 * A063794 A202942 A177400
Adjacent sequences: A071217 A071218 A071219 * A071221 A071222 A071223
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KEYWORD
| nonn
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AUTHOR
| Labos E. (labos(AT)ana.sote.hu), May 17 2002
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EXTENSIONS
| Edited and extended by Robert G. Wilson v (rgwv(AT)rgwv.com), Oct 07 2002
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