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Numbers k such that the deficiency of k plus the number of proper divisors of k is a prime number (see A152864).
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%I #10 Jan 06 2019 05:45:04

%S 2,3,4,5,6,7,9,10,11,13,14,16,17,18,19,20,21,22,23,26,27,28,29,31,34,

%T 37,38,41,43,45,46,47,49,52,53,55,57,58,59,61,62,64,67,70,71,73,74,75,

%U 76,77,79,82,83,86,88,89,91,93,94,95,97,99,101,103,104,106,107,109,110,111

%N Numbers k such that the deficiency of k plus the number of proper divisors of k is a prime number (see A152864).

%H B. D. Swan, <a href="/A152757/b152757.txt">Table of n, a(n) for n = 1..50000</a>

%p with(numtheory): a := proc (n) if isprime(2*n-sigma(n)+tau(n)-1) = true then n else end if end proc: seq(a(n), n = 1 .. 120); # _Emeric Deutsch_, Jan 08 2009

%Y Cf. A000005, A000203, A033879, A032741, A152770, A152864.

%K nonn

%O 1,1

%A _Omar E. Pol_, Dec 14 2008

%E Extended by _Emeric Deutsch_, Jan 08 2009

%E Name edited by _Jon E. Schoenfield_, Jan 06 2019