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Even numbers which are the sum of two odd abundant numbers.
2

%I #6 Jan 03 2013 20:03:50

%S 1890,2520,3150,3780,4410,5040,5670,6300,6720,6930,7350,7380,7560,

%T 7770,7980,8010,8190,8370,8400,8610,8640,8820,9000,9030,9240,9270,

%U 9360,9450,9630,9660,9870,9900,9990,10080,10260,10290,10500,10530,10620,10710

%N Even numbers which are the sum of two odd abundant numbers.

%C Every even number >= 3706141025766237065507279802221127212928 is the sum of two odd abundant numbers. The largest even number which does not appear in this sequence is unknown.

%H Donovan Johnson, <a href="/A168226/b168226.txt">Table of n, a(n) for n = 1..1000</a>

%e 945 is the smallest odd abundant number, so 945 + 945 = 1890 is the first term in the sequence.

%o (PARI) mx=66240; x=vector(mx); k=144; v=vector(k); c=0; forstep(i=945, mx-1, 2, if(sigma(i)-2*i>0, c++; v[c]=i)); for(i=1, k, for(j=i, k, s=v[i]+v[j]; if(s<=mx, x[s]=1, next(2)))); c=0; forstep(n=1890, mx, 2, if(x[n]==1, c++; write("b168226.txt", c " " n))) /* _Donovan Johnson_, Jan 03 2013 */

%Y Cf. A005231, A048260.

%K nonn

%O 1,1

%A _William Rex Marshall_, Nov 20 2009