A051271 Number of numbers either relatively prime to or divisors of primorial number(n).

3, 6, 16, 64, 512, 5824, 92288, 1659136, 36495872, 1021871104, 30656104448, 1103619690496, 44144787464192, 1854081073168384, 85287729365024768, 4434961926979649536, 257227791764816003072, 15433667505888952582144

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..350

Formula

A000005(A002110(n)) + A000010(A002110(n)); complementary to A045763(A002110).

Example

The 4th primorial (210) has 16 divisors and 48 coprimes, so a(4) = 16 + 48 = 64.

Mathematica

DivisorSigma[0, #]+EulerPhi[#]&/@Rest[FoldList[Times, 1, Prime[Range[20]]]] (* Harvey P. Dale, Sep 19 2013 *)

Crossrefs

Cf. A000005, A000010, A002110, A045763, A051272.

Sequence in context: A288850 A185629 A107885 * A028405 A328276 A191223

Adjacent sequences: A051268 A051269 A051270 * A051272 A051273 A051274

Keyword

nonn

Author

Labos Elemer

Status

approved