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)}.

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

Links

Table of n, a(n) for n=1..27.

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

Adjacent sequences: A129640 A129641 A129642 * A129644 A129645 A129646

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