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A247221
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Numbers k such that 2*k^2 + 1 divides 2^k + 1.
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2
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OFFSET
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1,3
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COMMENTS
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Numbers k such that (2^k + 1)/(2*k^2 + 1) is an integer.
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LINKS
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MATHEMATICA
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a247221[n_Integer] := Select[Range[n], Divisible[2^# + 1, 2*#^2 + 1] &]; a247221[2500000] (* Michael De Vlieger, Nov 30 2014 *)
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PROG
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(Magma) [n: n in [1..300000] | Denominator((2^n+1)/(2*n^2+1)) eq 1];
(PARI) for(n=0, 10^9, if(Mod(2, 2*n^2+1)^n==-1, print1(n, ", "))); \\ Joerg Arndt, Nov 30 2014
(Python)
A247221_list = [n for n in range(10**6) if pow(2, n, 2*n*n+1) == 2*n*n]
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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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