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 A051907 Number of ways to express 1 as the sum of distinct unit fractions such that the sum of the denominators is n. 4
 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 1, 0, 2, 0, 0, 0, 0, 2, 0, 1, 1, 1, 1, 0, 2, 0, 1, 1, 1, 2, 0, 4, 1, 3, 4, 0, 2, 0, 6, 0, 1, 2, 1, 3, 0, 4, 2, 1, 5, 5, 3, 2, 3, 3, 5, 5, 5, 2, 1, 12, 5, 4, 11, 4, 5, 2, 11, 3, 5 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,45 LINKS Seiichi Manyama, Table of n, a(n) for n = 1..150 EXAMPLE 1 = 1/2+1/4+1/9+1/12+1/18 = 1/2+1/5+1/6+1/12+1/20. The sum of the denominators of each of these is 45, these are the only 2 with sum of denominators = 45, so a(45)=2. CROSSREFS A051882 lists n such that a(n)=0. Cf. A051908. Sequence in context: A171919 A000089 A339430 * A178176 A093569 A073091 Adjacent sequences:  A051904 A051905 A051906 * A051908 A051909 A051910 KEYWORD nonn AUTHOR Jud McCranie, Dec 16 1999 EXTENSIONS R. L. Graham showed that a(n)>0 for n>77. STATUS approved

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Last modified July 29 22:13 EDT 2021. Contains 346346 sequences. (Running on oeis4.)