|
Search: id:A097978
|
|
|
| A097978 |
|
a(n) = least m such that m and m+n are both products of exactly n distinct primes. |
|
+0
3
|
|
| 1, 2, 33, 102, 1326, 115005, 31295895, 159282123, 9617162170, 1535531452026, 1960347077019695, 16513791577659519, 271518698440871310
(list; graph; listen)
|
|
|
OFFSET
|
0,2
|
|
|
COMMENT
|
Note that a(n) and a(n)+n are required to be squarefree. - David Wasserman (dwasserm(AT)earthlink.net), Feb 19 2008
If we change "exactly n" to "at least n", the sequence is still the same at least through a(12). - David Wasserman (dwasserm(AT)earthlink.net), Feb 19 2008
a(13) <= 592357638037885411965. - David Wasserman (dwasserm(AT)earthlink.net), Feb 19 2008
|
|
EXAMPLE
|
For the 3rd entry 102, we have {102=2*3*17, 102+3=3*5*7}, which is followed by {255=3*5*17, 255+3=2*3*43}, {282=2*3*47, 282+3=3*5*17}, ...
|
|
MATHEMATICA
|
f[n_] := Block[{lst = FactorInteger[n], a, b}, a = Plus @@ Last /@ lst; b = Length[lst]; If[a == b, b, 0]]; g[n_] := Block[{k = Product[ Prime[i], {i, n}]}, While[ f[k] != n || f[k] != f[k + n], k++ ]; k]; Do[ Print[ g[n]], {n, 1, 6}] (from Robert G. Wilson v Sep 11 2004)
|
|
CROSSREFS
|
Cf. A098515.
Cf. A098515, A135058.
Sequence in context: A003347 A065647 A041127 this_sequence A156369 A128152 A052403
Adjacent sequences: A097975 A097976 A097977 this_sequence A097979 A097980 A097981
|
|
KEYWORD
|
more,nonn
|
|
AUTHOR
|
Lekraj Beedassy (blekraj(AT)yahoo.com), Sep 07 2004
|
|
EXTENSIONS
|
Edited and extended by Mark Hudson (mrmarkhudson(AT)hotmail.com), Sep 08 2004
a(6)>30000000 - Robert G. Wilson v Sep 11 2004
More terms from David Wasserman (dwasserm(AT)earthlink.net), Feb 19 2008
|
|
|
Search completed in 0.002 seconds
|
