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Search: id:A108301
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| A108301 |
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Digital sum of the Fermat number 2^(2^n) + 1. |
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+0
1
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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
(list; graph; listen)
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OFFSET
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0,1
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COMMENT
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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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FORMULA
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a(n)=~4.5*A057755. - Robert G. Wilson v (rgwv(AT)rgwv.com), Jul 02 2005
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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); (Deutsch)
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MATHEMATICA
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f[n_] := Plus @@ IntegerDigits[2^(2^n)] + 1; Table[ f[n], {n, 0, 27}] (from Robert G. Wilson v (rgwv(AT)rgwv.com), Jul 02 2005)
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CROSSREFS
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Cf. A000215.
Sequence in context: A086661 A078065 A072655 this_sequence A095290 A080999 A077579
Adjacent sequences: A108298 A108299 A108300 this_sequence A108302 A108303 A108304
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KEYWORD
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base,nonn
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AUTHOR
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Jason Earls (zevi_35711(AT)yahoo.com), Jun 29 2005
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EXTENSIONS
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More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu) and Robert G. Wilson v (rgwv(AT)rgwv.com), Jul 02 2005
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