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A361891
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a(n) = S(7,n)/S(1,n), where S(r,n) = Sum_{k = 0..floor(n/2)} ( binomial(n,k) - binomial(n,k-1) )^r.
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6
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1, 1, 1, 43, 386, 9451, 246961, 6031627, 212559508, 6571985126, 243940325734, 9140730357409, 352312505157354, 14801600281919487, 600054439936968241, 26927918031565051915, 1149140935414286560040, 53804800109969394477580, 2401141625752684697505820
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OFFSET
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0,4
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COMMENTS
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For r a positive integer define S(r,n) = Sum_{k = 0..floor(n/2)} ( binomial(n,k) - binomial(n,k-1) )^r. Gould (1974) conjectured that S(3,n) was always divisible by S(1,n). See A183069 for {S(3,n)/S(1,n)}. In fact, calculation suggests that if r is odd then S(r,n) is always divisible by S(1,n). The present sequence is {S(7,n)/S(1,n)}.
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LINKS
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H. W. Gould, Problem E2384, Amer. Math. Monthly, 81 (1974), 170-171.
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FORMULA
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a(n) = 1/binomial(n,floor(n/2)) * Sum_{k = 0..floor(n/2)} ( (n - 2*k + 1)/(n - k + 1) * binomial(n,k) )^7.
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MAPLE
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seq(add( ( binomial(n, k) - binomial(n, k-1) )^7/binomial(n, floor(n/2)), k = 0..floor(n/2)), n = 0..20);
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CROSSREFS
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Cf. A003161 ( S(3,n) ), A003162 ( S(3,n)/S(1,n) ), A183069 ( S(3,2*n+1)/ S(1,2*n+1) ), A361887 ( S(5,n) ), A361888( S(5,n)/S(1,n) ), A361889 ( S(5,2*n-1)/S(1,2*n-1) ), A361890 ( S(7,n) ), A361892 ( S(7,2*n-1)/S(1,2*n-1) ).
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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