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A097978
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a(n) = least m such that m and m+n are both products of exactly n distinct primes.
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2
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1, 2, 33, 102, 1326, 115005, 31295895, 159282123, 9617162170, 1535531452026, 1960347077019695, 16513791577659519, 271518698440871310
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| 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
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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}, ...
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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)
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CROSSREFS
| Cf. A098515.
Cf. A098515, A135058.
Sequence in context: A003347 A065647 A041127 * A156369 A128152 A052403
Adjacent sequences: A097975 A097976 A097977 * A097979 A097980 A097981
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KEYWORD
| more,nonn
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AUTHOR
| Lekraj Beedassy (blekraj(AT)yahoo.com), Sep 07 2004
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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
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