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A297365 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
5, 11, 19, 71, 247, 271, 991, 2232, 6200, 8271, 10295, 16744, 18496, 18576, 25704, 26656, 102175, 122607, 166624, 225939, 301103, 747967, 7237384, 7302592, 15760224, 21770800, 28121184, 72967087, 98617024, 104577848, 173859007, 253496176, 335610184, 371191600 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The unitary version of A244439.

LINKS

Table of n, a(n) for n=1..34.

EXAMPLE

11 is in the sequence since uphi(11) * usigma(11) = 10 * 12 = uphi(12) * usigma(12) = 6 * 20 = 120.

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[10^6], aQ]

CROSSREFS

Cf. A034448, A047994, A244439.

Sequence in context: A152085 A267603 A323007 * A128927 A145934 A033913

Adjacent sequences:  A297362 A297363 A297364 * A297366 A297367 A297368

KEYWORD

nonn

AUTHOR

Amiram Eldar, Dec 29 2017

STATUS

approved

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Last modified November 14 20:15 EST 2019. Contains 329130 sequences. (Running on oeis4.)