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A053158 Sum of n and its cototient function value (A051953). 1
1, 3, 4, 6, 6, 10, 8, 12, 12, 16, 12, 20, 14, 22, 22, 24, 18, 30, 20, 32, 30, 34, 24, 40, 30, 40, 36, 44, 30, 52, 32, 48, 46, 52, 46, 60, 38, 58, 54, 64, 42, 72, 44, 68, 66, 70, 48, 80, 56, 80, 70, 80, 54, 90, 70, 88, 78, 88, 60, 104, 62, 94, 90, 96, 82, 112, 68, 104, 94, 116 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

For Mersenne primes and also for certain composites the values of this function are powers of 2.

LINKS

Table of n, a(n) for n=1..70.

FORMULA

a(n) = n + A051953(n) = 2n - EulerPhi(n).

EXAMPLE

a(127) = 254 - 126 = 128.

a(80) = 160 - 32 = 128.

a(2^s) = 3*2^(s-1).

PROG

(PARI) a(n) = 2*n - eulerphi(n); \\ Michel Marcus, Dec 19 2013

CROSSREFS

Cf. A000043, A000668, A001368, A051953.

Sequence in context: A175708 A023830 A063649 * A206924 A185443 A275258

Adjacent sequences:  A053155 A053156 A053157 * A053159 A053160 A053161

KEYWORD

nonn

AUTHOR

Labos Elemer, Feb 29 2000

STATUS

approved

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Last modified March 19 17:21 EDT 2019. Contains 321330 sequences. (Running on oeis4.)