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A341745
Numbers k such that 1/(1/phi(k) + 1/phi(k+1) + 1/phi(k+2) + 1/phi(k+3) + 1/phi(k+4)) is an integer.
3
30, 31, 35, 73, 19800, 291721, 298200, 539401, 3150841, 7650726, 12285002, 19571764, 21818162, 27017642, 33636241, 50441042, 50810762, 51760802, 71866082, 75479042, 78001562, 81235442, 104881681, 112123440, 125756282, 132055562, 137382482, 153742682, 158918762
OFFSET
1,1
MATHEMATICA
s = {}; v = EulerPhi @ Range[5]; Do[If[Numerator @ Total[1/v] == 1, AppendTo[s, k - 5]]; v = Join[Rest @ v, {EulerPhi[k]}], {k, 6, 10^7}]; s (* Amiram Eldar, Feb 18 2021 *)
PROG
(PARI) isok(k) = numerator(1/eulerphi(k) + 1/eulerphi(k+1) + 1/eulerphi(k+2) + 1/eulerphi(k+3) + 1/eulerphi(k+4)) == 1;
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Marcus, Feb 18 2021
EXTENSIONS
More terms from Jinyuan Wang, Feb 18 2021
STATUS
approved