The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A080767 A unitary phi reciprocal amicable number: consider two different numbers a, b which satisfy the following equation for some integer k: uphi(a)=uphi(b)=1/k*a*b/(a-b); or equivalently, 1/uphi(a)=1/uphi(b)=k*(-1/a+1/b); sequence gives b numbers. 2
 1, 3, 12, 20, 220, 144, 240, 5060, 5520, 5520, 10800, 11520, 8928, 15120, 31680, 33984, 56576, 60372, 39168, 65280, 80640, 149760, 149760, 169920, 281600, 398200, 664092, 669600, 940896, 1235520 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Here uphi(n)=A047994(n) is the unitary totient function: if n = Product p_i^e_i, uphi(n) = Product (p_i^e_i - 1). LINKS CROSSREFS Cf. A047994, A080766, A080768, A067739, A067741. Sequence in context: A143268 A193558 A256131 * A043465 A074276 A055041 Adjacent sequences: A080764 A080765 A080766 * A080768 A080769 A080770 KEYWORD nonn AUTHOR EXTENSIONS Kohmoto found 2nd, 6th, 13th, 25th terms. Dean Hickerson calculated the other terms. STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified January 27 20:21 EST 2023. Contains 359849 sequences. (Running on oeis4.)