A280981 Partial products of A049820; a(1) = a(2) = 1.

1, 1, 1, 1, 3, 6, 30, 120, 720, 4320, 38880, 233280, 2566080, 25660800, 282268800, 3104956800, 46574352000, 558892224000, 9501167808000, 133016349312000, 2261277938304000, 40703002889472000, 854763060678912000, 13676208970862592000, 300876597358977024000

Offset

1,5

Links

Table of n, a(n) for n=1..25.

Formula

a(1) = a(2) = 1; for n>2, a(n) = Product_{i=3..n} A049820(i).

Mathematica

FoldList[#1 #2 &, Table[Boole[n <= 2] + n - DivisorSigma[0, n], {n, 25}]] (* Michael De Vlieger, Jan 11 2017 *)

Prog

(Magma) [1, 1] cat [&*[#[c: c in [1..k] | k mod c ne 0]: k in [3..n]]: n in [3..100]]

Crossrefs

Cf. A049820(n) = number of nondivisors of n.

Cf. A049820, A161664.

Sequence in context: A350756 A090932 A361864 * A265376 A318431 A157534

Adjacent sequences: A280978 A280979 A280980 * A280982 A280983 A280984

Keyword

nonn

Author

Jaroslav Krizek, Jan 11 2017

Status

approved