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A051271 Number of numbers either relatively prime to or divisors of primorial number(n). 2
3, 6, 16, 64, 512, 5824, 92288, 1659136, 36495872, 1021871104, 30656104448, 1103619690496, 44144787464192, 1854081073168384, 85287729365024768, 4434961926979649536, 257227791764816003072, 15433667505888952582144 (list; graph; refs; listen; history; text; internal format)
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

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Last modified October 21 07:07 EDT 2019. Contains 328292 sequences. (Running on oeis4.)