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A129643
a(1)=1. a(n) = a(n-1)*(b(n-1)+1), where {b(k)} is the concatenated list of the positive divisors of the terms of {a(k)}.
2
1, 2, 4, 12, 24, 72, 360, 720, 2160, 8640, 43200, 302400, 3931200, 7862400, 23587200, 94348800, 471744000, 3302208000, 29719872000, 386358336000, 9658958400000, 19317916800000, 57953750400000, 231815001600000, 1159075008000000, 8113525056000000, 73021725504000000
OFFSET
1,2
EXAMPLE
The list of positive divisors of the terms of {a(k)} is (sequence A129644) 1;1,2;1,2,4;1,2,3,4,6,12;.... The n-th term of {a(k)} is product{k=1 to n-1}(A129644(k)+1).
MAPLE
A129643 := proc(nmax) local a, b, n, a_1; a := [1] ; b := [1] ; while nops(a) < nmax do n := nops(a)+1 ; a_1 := op(-1, a) ; a := [op(a), a_1*(op(n-1, b)+1)] ; a_1 := op(-1, a) ; if nops(b) < nmax then b := [op(b), op(numtheory[divisors](a_1))] ; fi ; od: RETURN(a) ; end: A129643(40) ; # R. J. Mathar, Oct 16 2007
CROSSREFS
Cf. A129644.
Sequence in context: A161894 A062177 A348642 * A332644 A200337 A367173
KEYWORD
nonn,base
AUTHOR
Leroy Quet, Apr 25 2007
EXTENSIONS
More terms from R. J. Mathar, Oct 16 2007
Corrected by N. J. A. Sloane, Nov 04 2007
STATUS
approved