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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 (list; graph; refs; listen; history; text; internal format)
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

LINKS

Table of n, a(n) for n=1..17.

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: A160038 A322746 A184274 * A189412 A246192 A246612

Adjacent sequences:  A093453 A093454 A093455 * A093457 A093458 A093459

KEYWORD

nonn,less

AUTHOR

Amarnath Murthy, Apr 03 2004

EXTENSIONS

More terms from Stefan Steinerberger, Apr 02 2006

STATUS

approved

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Last modified May 28 14:47 EDT 2020. Contains 334684 sequences. (Running on oeis4.)