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A160921
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Numbers k such that k / (A000005(k)*(A000005(k)+1)/2) is an integer.
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2
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1, 3, 10, 63, 147, 156, 225, 234, 408, 600, 680, 684, 952, 1014, 1496, 1500, 1768, 2176, 2584, 3128, 3944, 4216, 4224, 4275, 5032, 5576, 5848, 5880, 6392, 6498, 6660, 6875, 7208, 8024, 8296, 8379, 9112, 9324, 9656, 9840, 9928
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OFFSET
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1,2
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LINKS
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MAPLE
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n :=1 :
for k from 1 to 50000 do
printf("%d %d\n", n, k) ;
n := n+1 ;
end if;
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MATHEMATICA
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t[n_] := n*(n + 1)/2; Select[Range[10^4], Divisible[#, t[DivisorSigma[0, #]]] &] (* Amiram Eldar, Jan 17 2021 *)
dsiQ[n_]:=With[{d=DivisorSigma[0, n]}, IntegerQ[n/((d(d+1))/2)]]; Select[Range[10000], dsiQ] (* Harvey P. Dale, Aug 20 2023 *)
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PROG
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(PARI) lista(nn) = {for (n=1, nn, if (2*n % (numdiv(n)*(numdiv(n)+1)) == 0, print1(n, ", ")); ); } \\ Michel Marcus, Jun 02 2013
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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