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 A187743 Smallest number which is an unordered sum of two odd abundant numbers in exactly n ways. 1
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The first 10000 terms are all divisible by 210. LINKS Donovan Johnson, Table of n, a(n) for n = 1..10000 EXAMPLE 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. PROG (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])) CROSSREFS Cf. A005231, A168226. Sequence in context: A279621 A168226 A151721 * A251829 A251822 A251821 Adjacent sequences: A187740 A187741 A187742 * A187744 A187745 A187746 KEYWORD nonn AUTHOR Donovan Johnson, Jan 03 2013 STATUS approved

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Last modified May 19 13:25 EDT 2024. Contains 372694 sequences. (Running on oeis4.)