|
Search: id:A121315
|
|
|
| A121315 |
|
Products of two consecutive prime powers. |
|
+0
2
|
|
| 2, 6, 12, 20, 35, 56, 72, 99, 143, 208, 272, 323, 437, 575, 675, 783, 899, 992, 1184, 1517, 1763, 2021, 2303, 2597, 3127, 3599, 3904, 4288, 4757, 5183, 5767, 6399, 6723, 7387, 8633, 9797, 10403, 11021, 11663, 12317, 13673, 15125, 15875, 16256, 16768
(list; graph; listen)
|
|
|
OFFSET
|
1,1
|
|
|
COMMENT
|
For some algorithms for finding A034699(n), the numbers in this sequence represent a worst case scenario of execution time.
|
|
FORMULA
|
a(n) = A000961(n)*A000961(n+1)
|
|
EXAMPLE
|
437 = 19*23 and none of the intervening integers (20,21,22) are prime powers.
|
|
MATHEMATICA
|
t = Join[{1}, Select[Range[2, 131], Mod[ #, # - EulerPhi[ # ]] == 0 &]]; Most@t*Rest@t - Robert G. Wilson v, Sept 02 2006
|
|
CROSSREFS
|
Cf. A000961, A034699.
Sequence in context: A002378 A005991 A003274 this_sequence A078878 A095361 A095362
Adjacent sequences: A121312 A121313 A121314 this_sequence A121316 A121317 A121318
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Paul Richards (pr(AT)paulrichards.me.uk), Aug 28 2006
|
|
EXTENSIONS
|
More terms from Robert G. Wilson v, Sept 02 2006
|
|
|
Search completed in 0.002 seconds
|
