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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 (list; graph; refs; listen; history; text; internal format)
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: A135139 A161894 A062177 * A200337 A320931 A096421

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

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Last modified December 7 22:29 EST 2019. Contains 329850 sequences. (Running on oeis4.)