The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A067798 Numbers n such that phi(n)+phi(n+1)=n+1. 1
 1, 2, 3, 5, 9, 15, 21, 35, 39, 45, 75, 99, 135, 231, 255, 363, 483, 765, 855, 1295, 1599, 2015, 2115, 4335, 6783, 9999, 14399, 16095, 16599, 18495, 30495, 53823, 62799, 63455, 65535, 77615, 155319, 186999, 196095, 327675, 589815, 686735, 722015 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Giovanni Resta, Table of n, a(n) for n = 1..76 FORMULA {n: A000010(n) = A051953(n+1)}. - Omar E. Pol, May 15 2016 MATHEMATICA Select[Range[10^5], Plus @@ EulerPhi[{#, # + 1}] == # + 1 &] (* Giovanni Resta, May 15 2016 *) PROG (PARI) isok(n) = eulerphi(n)+eulerphi(n+1) == n+1; \\ Michel Marcus, May 15 2016 CROSSREFS Cf. A000010, A051953, A067796. Sequence in context: A101461 A085897 A306829 * A205536 A281704 A074693 Adjacent sequences:  A067795 A067796 A067797 * A067799 A067800 A067801 KEYWORD nonn AUTHOR Benoit Cloitre, Feb 07 2002 EXTENSIONS More terms from Dean Hickerson, Feb 16 2002 STATUS approved

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

Last modified August 13 06:22 EDT 2020. Contains 336442 sequences. (Running on oeis4.)