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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 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.)