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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A297366 Numbers n such that uphi(n) + usigma(n) = uphi(n+1) + usigma(n+1), where uphi is the unitary totient function (A047994) and usigma the sum of unitary divisors (A034448). 0
6, 10, 12, 15, 18, 22, 24, 26, 28, 36, 40, 46, 48, 52, 58, 63, 72, 80, 82, 88, 96, 100, 106, 108, 112, 124, 136, 148, 162, 166, 172, 178, 192, 196, 226, 232, 242, 250, 262, 268, 285, 288, 292, 316, 346, 352, 358, 382, 388, 400, 432, 448, 466, 478, 486, 502 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The unitary version of A145749.

LINKS

Table of n, a(n) for n=1..56.

EXAMPLE

6 is in the sequence since uphi(6) + usigma(6) = 2 + 12 = uphi(7) + usigma(7) = 6 + 8 = 14.

MATHEMATICA

usigma[n_] := If[n == 1, 1, Times @@ (1 + Power @@@ FactorInteger[n])];

uphi[n_] := (Times @@ (Table[#[[1]]^#[[2]] - 1, {1}] & /@ FactorInteger[n]))[[1]]; u[n_] := uphi[n]+usigma[n]; aQ[n_] := u[n] == u[n + 1]; Select[Range[10^3], aQ]

CROSSREFS

Cf. A034448, A047994, A145749.

Sequence in context: A279550 A143958 A294278 * A325472 A305188 A270364

Adjacent sequences:  A297363 A297364 A297365 * A297367 A297368 A297369

KEYWORD

nonn

AUTHOR

Amiram Eldar, Dec 29 2017

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.

License Agreements, Terms of Use, Privacy Policy. .

Last modified April 19 22:40 EDT 2021. Contains 343117 sequences. (Running on oeis4.)