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A090907 Ratio of products of successive rows of the irregular triangle defined in A090905. 4
2, 6, 140, 1287, 2139552000, 2949442889323392, 322686644032484531917367528014184448000000 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Conjecture: For n > 4 the last term of the n-th group is 2p where p is the largest prime in the (n-1)th group. And these are the Bertrand primes.
LINKS
EXAMPLE
a(1)=(2!/1!)*(0!/1!)
a(2)=(4!/2!)*(1!/2!)
a(3)=(8!/4!)*(2!/4!)
a(4)=(14!/8!)*(4!/8!)
a(5)=(26!/14!)*(8!/14!)
a(6)=(46!/26!)*(14!/26!)
For n>=6 we have a(n)= ((2*A006992(n))!/(2*A006992(n-1))!)*((2*A006992(n-2))!/(2*A006992(n-1))!), verified for 4<n<21
CROSSREFS
Sequence in context: A254223 A206849 A368395 * A159478 A047937 A027731
KEYWORD
nonn
AUTHOR
Amarnath Murthy, Dec 13 2003
EXTENSIONS
Edited by Mohammed Bouayoun (bouyao(AT)wanadoo.fr), Mar 05 2004
STATUS
approved

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Last modified June 20 23:18 EDT 2024. Contains 373535 sequences. (Running on oeis4.)