A073543 Numbers k such that 1/(1/phi(k) + 1/phi(k+1) + 1/phi(k+2)) is an integer.

12, 36, 37, 72, 73, 86, 95, 181, 192, 482, 540, 541, 560, 637, 813, 1152, 1620, 1621, 1683, 2017, 2101, 2283, 2557, 2592, 2642, 2916, 3031, 3032, 3061, 3381, 3624, 3625, 4357, 5077, 5186, 5581, 6337, 6661, 7417, 8100, 9118, 9181, 9299, 9720, 9901

Offset

1,1

Links

Seiichi Manyama, Table of n, a(n) for n = 1..10000

Example

1/phi(2283)+1/phi(2284)+1/phi(2285) = 1/1520+1/1140+1/1824 = 1/480 so 2283 is in the sequence.

Mathematica

Select[Range[10000], IntegerQ[1/Sum[1/EulerPhi[ #+i], {i, 0, 2}]]&]

Prog

(PARI) isok(k) = numerator(1/eulerphi(k) + 1/eulerphi(k+1) + 1/eulerphi(k+2)) == 1; \\ Michel Marcus, Feb 18 2021

Crossrefs

Cf. A000010, A073542, A073544, A341745, A341799.

Sequence in context: A038006 A205967 A203378 * A349020 A074234 A076515

Adjacent sequences: A073540 A073541 A073542 * A073544 A073545 A073546

Keyword

easy,nonn

Author

Benoit Cloitre, Aug 27 2002

Extensions

Edited by Dean Hickerson, Sep 03 2002

Status

approved