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Search: id:A086714
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A086714 a(1)=4, a(n)=a(n-1)*(a(n-1)-1)/2. +0
1
4, 6, 15, 105, 5460, 14903070, 111050740260915, 6166133456248548335768188155, 19010600900133834176644234577571914951562754277857057935, 18070147329208467311897260063361878628494991729486234862358886529150876544280110\ 7068736938092643935008044703145 (list; graph; listen)
OFFSET

1,1

EXAMPLE

a(2)=a(1)*(a(1)-1)/2 = 4*3/2 = 6

PROGRAM

(PARI) v=vector(10, i, (i==1)*4); for(i=2, 10, v[i]=v[i-1]*(v[i-1]-1)/2); v

CROSSREFS

Sequence in context: A007135 A073603 A064910 this_sequence A009463 A066260 A141042

Adjacent sequences: A086711 A086712 A086713 this_sequence A086715 A086716 A086717

KEYWORD

nonn

AUTHOR

Jon Perry (perry(AT)globalnet.co.uk), Jul 29 2003

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Last modified November 25 20:09 EST 2009. Contains 167514 sequences.


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