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A093456
Product of composite numbers among next n numbers.
2
1, 1, 24, 720, 2520, 120960, 259459200, 1357171200, 4929724800, 42608389824000, 11912739135897600, 59907396092544000, 20458385028297216000, 7926428532945162240000, 4693751193479184764928000, 328774885640356760904499200000, 12797917159224592605450240000
OFFSET
1,3
COMMENTS
Conjecture: There are finitely many numbers such that a(n)is not == 0 (mod a(n-1). (Also mentioned in A093455.)
Product of all composite numbers between n*(n-1)/2+1 and n*(n+1)/2 (including boundaries). - Stefan Steinerberger, Apr 02 2006
EXAMPLE
a(5) = 12*14*15 = 2520.
MATHEMATICA
Table[a := Range[n*(n - 1)/2 + 1, n*(n + 1)/2]; b := Select[a, Not[PrimeQ[ # ]] &]; Product[b[[i]], {i, 1, Length[b]}], {n, 1, 20}] (* Stefan Steinerberger, Apr 02 2006 *)
CROSSREFS
Cf. A093455.
Sequence in context: A322746 A367330 A184274 * A189412 A246192 A246612
KEYWORD
nonn,less
AUTHOR
Amarnath Murthy, Apr 03 2004
EXTENSIONS
More terms from Stefan Steinerberger, Apr 02 2006
STATUS
approved