A280458 Partial products of A023896.

1, 1, 3, 12, 120, 720, 15120, 241920, 6531840, 130636800, 7185024000, 172440576000, 13450364928000, 564915326976000, 33894919618560000, 2169274855587840000, 295021380359946240000, 15931154539437096960000, 2724227426243743580160000, 217938194099499486412800000

Offset: 1

Author

Jaroslav Krizek, Jan 03 2017

Keywords

• nonn

Crossrefs

Cf. A023896 (sum of totatives of n), A213544 (partial sums of A023896).

Programs

Magma

[&*[&+[h: h in [1..k] | GCD(h,k) eq 1]: k in [1..n]]: n in [1..100]];

Mathematica

FoldList[#1 #2 &, Table[Ceiling[(n EulerPhi@ n)/2], {n, 20}]] (* Michael De Vlieger, Jan 03 2017 *)

Formula

a(n) = Sum_{i=1..n} A023896(i).