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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A353679 Odd numbers k for which phi(k) = phi(sigma(k)). 3
 1, 3, 15, 39, 45, 111, 117, 175, 183, 195, 219, 333, 357, 471, 549, 555, 579, 585, 657, 831, 915, 939, 1071, 1095, 1191, 1263, 1371, 1413, 1443, 1623, 1665, 1737, 1839, 1983, 2019, 2199, 2271, 2275, 2295, 2355, 2379, 2493, 2631, 2745, 2817, 2847, 2895, 2991, 3279, 3285, 3459, 3573, 3603, 3639, 3711, 3789, 3963 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Table of n, a(n) for n=1..57. Index entries for sequences where odd perfect numbers must occur, if they exist at all Index entries for sequences related to sigma(n) MATHEMATICA Select[Range[1, 4000, 2], EulerPhi[#] == EulerPhi[DivisorSigma[1, #]] &] (* Amiram Eldar, May 06 2022 *) PROG (PARI) A353680(n) = ((n%2) && (eulerphi(sigma(n))==eulerphi(n))); isA353679(n) = A353680(n); CROSSREFS Odd terms in A006872. Cf. A000010, A000035, A000203, A062401, A353637, A353680 (characteristic function). Sequence in context: A185541 A176661 A117561 * A065765 A318738 A146853 Adjacent sequences: A353676 A353677 A353678 * A353680 A353681 A353682 KEYWORD nonn AUTHOR Antti Karttunen, May 06 2022 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 September 28 20:32 EDT 2023. Contains 365737 sequences. (Running on oeis4.)