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A063785 Numbers n such that sigma(n) = 2n + omega(n), where omega(n) is the number of distinct prime divisors of n. 0
20, 104, 464, 1952, 4030, 5830, 130304, 522752, 1848964, 8382464, 134193152 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

It is easily proved that if 2^m-3 is prime then 2^(m-1)*(2^m-3) is in the sequence. - Farideh Firoozbakht, Feb 12 2008

LINKS

Table of n, a(n) for n=1..11.

PROG

(PARI) for(n=1, 10^8, if(sigma(n)==2*n+omega(n), print(n)))

CROSSREFS

Cf. A045768.

Sequence in context: A189950 A045768 A088831 * A181703 A187756 A248087

Adjacent sequences:  A063782 A063783 A063784 * A063786 A063787 A063788

KEYWORD

nonn

AUTHOR

Jason Earls, Aug 17 2001

STATUS

approved

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Last modified October 13 23:56 EDT 2019. Contains 327983 sequences. (Running on oeis4.)