A072161 Denominator of Sum_{k=1..n} phi(k)/k^4.

1, 16, 1296, 10368, 6480000, 6480000, 15558480000, 124467840000, 3360631680000, 3360631680000, 49203008426880000, 49203008426880000, 1405287123680119680000, 1405287123680119680000, 1405287123680119680000, 11242296989440957440000

Offset

1,2

Links

G. C. Greubel, Table of n, a(n) for n = 1..592

Example

1, 17/16, 1409/1296, 11353/10368, 7137097/6480000, 7147097/6480000, ...

Maple

with(numtheory); seq(denom(add(phi(k)/k^4, k = 1..n)), n = 1..25); # G. C. Greubel, Aug 26 2019

Mathematica

Table[Denominator[Sum[EulerPhi[k]/k^4, {k, n}]], {n, 25}] (* G. C. Greubel, Aug 26 2019 *)

Prog

(PARI) a(n) = denominator( sum(k=1, n, eulerphi(k)/k^4)); \\ G. C. Greubel, Aug 26 2019
(Magma) [Denominator( &+[EulerPhi(k)/k^4: k in [1..n]] ): n in [1..25]]; // G. C. Greubel, Aug 26 2019
(Sage) [denominator( sum(euler_phi(k)/k^4 for k in (1..n)) ) for n in (1..25)] # G. C. Greubel, Aug 26 2019
(GAP) List([1..25], n-> DenominatorRat( Sum([1..n], k-> Phi(k)/k^3) ) ); # G. C. Greubel, Aug 26 2019

Crossrefs

Cf. A072160.

Sequence in context: A224105 A224098 A016828 * A173544 A248619 A334585

Adjacent sequences: A072158 A072159 A072160 * A072162 A072163 A072164

Keyword

nonn,frac

Author

N. J. A. Sloane, Jun 28 2002

Status

approved