A187743 Smallest number which is an unordered sum of two odd abundant numbers in exactly n ways.

1890, 3150, 4410, 5670, 6930, 8190, 9450, 10710, 11970, 12600, 14490, 13860, 15750, 17010, 20160, 19530, 22050, 20790, 23940, 24570, 26460, 28350, 28980, 64680, 27720, 32130, 32760, 38430, 39690, 40320, 34650, 51660, 53550, 56700, 41580, 58590, 48510, 70560

Offset: 1

Author

Donovan Johnson, Jan 03 2013

Keywords

• nonn

Comments

The first 10000 terms are all divisible by 210.

Examples

			Summands are odd abundant numbers.
a(1) = 1890 = 945 + 945.
a(2) = 3150 = 945 + 2205 = 1575 + 1575.
a(3) = 4410 = 945 + 3465 = 1575 + 2835 = 2205 + 2205.
a(4) = 5670 = 945 + 4725 = 1575 + 4095 = 2205 + 3465 = 2835 + 2835.
		

Links

• Donovan Johnson, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A005231, A168226.

Programs

PARI

/* finds first 1000 terms */ mx=4616430; ct=vector(mx); k=9384; v=vector(k); n=vector(1000); 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, ct[s]++, next(2)))); forstep(i=1890, mx, 2, if(ct[i]>0 && ct[i]<=1000 && n[ct[i]]==0, n[ct[i]]=i)); for(i=1, 1000, write("b187743.txt", i " " n[i]))