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A054901
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Numbers of the form 2^i*5^j where i+j is even.
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1
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1, 4, 10, 16, 25, 40, 64, 100, 160, 250, 256, 400, 625, 640, 1000, 1024, 1600, 2500, 2560, 4000, 4096, 6250, 6400, 10000, 10240, 15625, 16000, 16384, 25000, 25600, 40000, 40960, 62500, 64000, 65536, 100000, 102400, 156250, 160000, 163840
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OFFSET
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1,2
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COMMENTS
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m is in the sequence iff m/10 is already in the sequence or m is a power of 4 or 25.
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LINKS
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FORMULA
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MATHEMATICA
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max = 200000; Reap[Do[k = 2^i*5^j; If[k <= max && EvenQ[i + j], Sow[k]], {i, 0, Log[2, max] // Ceiling}, {j, 0, Log[5, max] // Ceiling}]][[2, 1]] // Union (* Amiram Eldar, Feb 18 2021 after Jean-François Alcover at A036667 *)
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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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STATUS
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approved
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