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A244673
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Numbers k that divide 2^k + 4.
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8
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1, 2, 3, 4, 20, 260, 740, 2132, 2180, 5252, 43364, 49268, 49737, 80660, 130052, 293620, 542852, 661412, 717027, 865460, 1564180, 2185220, 2192132, 2816372, 3784916, 4377620, 4427540, 5722004, 6307652, 6919460, 8765252, 9084452, 9498260, 9723611, 11346260, 12208820, 12220132
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OFFSET
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1,2
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LINKS
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EXAMPLE
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2^2 + 4 = 8 is divisible by 2. Thus 2 is a term of this sequence.
2^3 + 4 = 12 is divisible by 3. Thus 3 is a term of this sequence.
2^4 + 4 = 20 is divisible by 4. Thus 4 is a term of this sequence.
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MAPLE
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Alternative:
select(n -> 4 + 2&^n mod n = 0, [$1..10^5]); # Robert Israel, Jul 15 2014
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MATHEMATICA
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Select[Range[1000], Mod[2^# + 4, #] == 0 &] (* Alonso del Arte, Jul 14 2014 *)
Join[{1, 2, 3}, Select[Range[1223*10^4], PowerMod[2, #, #]==#-4&]] (* Harvey P. Dale, Jan 16 2023 *)
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PROG
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(PARI) for(n=1, 10^8, if(Mod(2, n)^n+4==0, print1(n, ", "))) \\ Jens Kruse Andersen, Jul 15 2014
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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