A130479 a(n) = smallest positive integer such that lcm(a(0),a(1),a(2),..,a(n)) is a multiple of n!!, for all nonnegative integers n. (n!! = n(n-2)(n-4)...(2 or 1).).

1, 1, 2, 3, 8, 5, 16, 7, 128, 27, 256, 11, 1024, 13, 2048, 2025, 32768, 17, 65536, 19, 262144, 11907, 524288, 23, 4194304, 625, 8388608, 6561, 33554432, 29, 67108864, 31, 2147483648, 2381643, 4294967296, 1071875, 17179869184, 37, 34359738368

Offset

0,3

Links

Table of n, a(n) for n=0..38.

Example

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

Maple

A130479 := proc(nmax) local a, n, df, k, f, p, l; 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; RETURN(a) ; end: A130479(60) ; # R. J. Mathar, Oct 16 2007

Crossrefs

Cf. A006882 (n!!), A130480.

Sequence in context: A343072 A352844 A095168 * A272878 A094181 A004730

Adjacent sequences: A130476 A130477 A130478 * A130480 A130481 A130482

Keyword

nonn

Author

Leroy Quet, May 29 2007

Extensions

More terms from R. J. Mathar, Oct 16 2007

Status

approved