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A071395 Primitive abundant numbers (abundant numbers all of whose proper divisors are deficient numbers). 6

%I

%S 20,70,88,104,272,304,368,464,550,572,650,748,836,945,1184,1312,1376,

%T 1430,1504,1575,1696,1870,1888,1952,2002,2090,2205,2210,2470,2530,

%U 2584,2990,3128,3190,3230,3410,3465,3496,3770,3944,4030,4070,4095,4216,4288

%N Primitive abundant numbers (abundant numbers all of whose proper divisors are deficient numbers).

%D Guy, R. K. Unsolved Problems in Number Theory, 2nd ed. New York: Springer-Verlag, p. 46, also section B2, 1994.

%H Donovan Johnson, <a href="/A071395/b071395.txt">Table of n, a(n) for n = 1..10000</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/PrimitiveAbundantNumber.html">Primitive Abundant Number</a>

%o (PARI) isA071395(v) = {if (sigma(v) <= 2*v, return (0)); fordiv (v, d, if ((d != v) && (sigma(d) >= 2*d), return (0));); return (1);} \\ _Michel Marcus_, Mar 10 2013

%Y Cf. A006038, A000396, A005100, A005101.

%K nonn

%O 1,1

%A Joe McCauley (mccauley(AT)davesworld.net), Jun 12 2002

%E Offset corrected by _Donovan Johnson_, Aug 28 2011

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Last modified September 1 19:46 EDT 2014. Contains 246317 sequences.