|
Search: id:A071220
|
|
|
| A071220 |
|
Numbers n such that prime(n) + prime(n+1) is a cube. |
|
+0
3
|
|
| 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; listen)
|
|
|
OFFSET
|
1,1
|
|
|
COMMENT
|
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.
|
|
FORMULA
|
A001043(x)=m^3 for some m; if p(x+1)+p(x) is a cube, then x is here.
|
|
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
|
|
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}]
|
|
CROSSREFS
|
Cf. A064397, A074925, A074924, A001043.
Adjacent sequences: A071217 A071218 A071219 this_sequence A071221 A071222 A071223
Sequence in context: A113633 A009674 A143598 this_sequence A063794 A085602 A058502
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Labos E. (labos(AT)ana.sote.hu), May 17 2002
|
|
EXTENSIONS
|
Edited and extended by Robert G. Wilson v (rgwv(AT)rgwv.com), Oct 07 2002
|
|
|
Search completed in 0.002 seconds
|
