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A108301
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Digital sum of the Fermat number 2^(2^n) + 1.
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0
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3, 5, 8, 14, 26, 59, 89, 167, 377, 734, 1376, 2741, 5624, 11120, 22166, 44222, 88262, 176180, 353042, 707648, 1419974, 2836751, 5679620, 11365592, 22723865, 45445442, 90899234, 181828850
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OFFSET
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0,1
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COMMENTS
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a(0), a(1), a(5), a(6), a(7) and a(11) are primes. Are there any more?
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LINKS
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FORMULA
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EXAMPLE
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a(5)=59 because 2^(2^5) + 1 = 4294967297 and the sum of those decimal digits is 59.
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MAPLE
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a:=proc(n) local nn, z: nn:=convert(2^(2^n)+1, base, 10): z:=nops(nn): add(nn[j], j=1..z) end: seq(a(n), n=0..22); # Emeric Deutsch
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MATHEMATICA
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f[n_] := Plus @@ IntegerDigits[2^(2^n)] + 1; Table[ f[n], {n, 0, 27}] (* Robert G. Wilson v, Jul 02 2005 *)
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CROSSREFS
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KEYWORD
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base,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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