A130480 - OEIS

%I #8 Aug 24 2015 02:34:10

%S 1,1,2,6,24,120,240,1680,13440,120960,241920,2661120,10644480,

%T 138378240,276756480,4151347200,66421555200,1129166438400,

%U 2258332876800,42908324659200,171633298636800,3604299271372800,7208598542745600

%N a(n) = lcm(b(0),b(1),b(2),...,b(n)), where b(m) = A130479(m).

%e a(6) = lcm(b(0),b(1),b(2),b(3),b(4),b(5),b(6)) = lcm(1,1,2,3,8,5,16) = 240. 6!! = 6*4*2 = 48 divides 240.

%p A130480 := proc(nmax) local a,n,df,k,f,p,l,b; a := [1,1] ; while nops(a)< nmax do n := nops(a) ; df := ifactors(doublefactorial(n))[2] ; l := ilcm(op(a)) ; k := 1 ; for f in df do p := op(1,f)^op(2,f) ; if l mod p <> 0 then k := k*p ; fi; od: a := [op(a),k] ; od; b := [] ; for i from 1 to nops(a) do b := [op(b),ilcm(op(1..i,a))] ; od: RETURN(b) ; end: A130480(30) ; # _R. J. Mathar_, Oct 16 2007

%Y Cf. A130479.

%K nonn

%O 0,3

%A _Leroy Quet_, May 29 2007

%E More terms from _R. J. Mathar_, Oct 16 2007