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A067739 Integers x such that for some integer y we have uphi(x) = uphi(y) = x-y, where uphi(n) = A047994(n) is the unitary totient function: If n = Product p_i^e_i, uphi(n) = Product (p_i^e_i - 1). 5
2, 60, 390, 840, 2310, 2910, 4386, 6090, 10374, 11220, 13860, 21882, 33654, 51090, 82680, 114294, 140910, 157080, 159530, 168630, 203190, 272514, 282170, 318318, 332010, 362670, 367080, 393414, 403130, 411990, 434070, 492882, 499590, 585390 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Donovan Johnson, Table of n, a(n) for n = 1..300

MATHEMATICA

uphi[n_] := Times@@(Power@@#-1&/@FactorInteger[n]); For[x=1, True, x++, If[uphi[y=x-(u=uphi[x])]==u, Print[{x, y}]]]

CROSSREFS

Cf. A047994, A067741.

Sequence in context: A141055 A275819 A048541 * A187626 A059934 A006333

Adjacent sequences:  A067736 A067737 A067738 * A067740 A067741 A067742

KEYWORD

nonn

AUTHOR

Yasutoshi Kohmoto

EXTENSIONS

Edited by Dean Hickerson, Mar 07 2002

Offset corrected by Donovan Johnson, May 04 2013

STATUS

approved

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Last modified March 2 19:18 EST 2021. Contains 341756 sequences. (Running on oeis4.)