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Search: id:A110351
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| A110351 |
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Least sum (n+1) + (n+2) + ... + (n+k) which is a multiple of the n-th triangular number n(n+1)/2. |
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+0
3
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| 2, 3, 30, 110, 30, 84, 1148, 1980, 585, 935, 462, 702, 2912, 105, 3120, 32504, 9027, 11457, 2660, 420, 2772, 26312, 16560, 19800, 44525, 52299, 17388, 20300, 10005, 11625, 460784, 61248, 11220, 2975, 24570, 43290, 220742, 29640, 4680, 188600
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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a(3) = 4 + 5 + 6 + 7 + 8 = 30 = 5*6, T(3) = 3*4/2 = 6.
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MAPLE
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a:=proc(n) local p, m: p:=proc(k) if type(sum(n+j, j=1..k)/(n*(n+1)/2), integer)=true then k else fi end: m:=[seq(p(k), k=1..1200)][1]: sum(n+j, j=1..m) end: seq(a(n), n=1..45); (Deutsch)
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MATHEMATICA
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Do[t = n*(n+1)/2; k = 1; While[Mod[k*n + k*(k+1)/2, t] > 0, k++ ]; Print[k*n + k*(k+1)/2], {n, 1, 50}] (Propper)
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CROSSREFS
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Cf. A110352, A110353.
Sequence in context: A167453 A095927 A137981 this_sequence A088115 A048986 A093712
Adjacent sequences: A110348 A110349 A110350 this_sequence A110352 A110353 A110354
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KEYWORD
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nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Jul 21 2005
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EXTENSIONS
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More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu) and Ryan Propper (rpropper(AT)stanford.edu), Aug 08 2005
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