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A109750
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Admirable triangular numbers.
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0
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OFFSET
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1,1
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COMMENTS
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No further term between 523776 and 4050045000. - R. J. Mathar, Feb 11 2008
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LINKS
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FORMULA
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EXAMPLE
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a(1) = 66 because 11*(11+1)/2 = 66 and 1+2+3+11+22+33-6 = 66.
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MATHEMATICA
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admQ[n_] := (ab = DivisorSigma[1, n] - 2 n) > 0 && EvenQ[ab] && ab/2 < n && Divisible[n, ab/2]; Select[Accumulate[Range[1024]], admQ] (* Amiram Eldar, Aug 05 2023 *)
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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STATUS
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approved
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