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A108301 Digital sum of the Fermat number 2^(2^n) + 1. 0
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; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

a(0), a(1), a(5), a(6), a(7) and a(11) are primes. Are there any more?

LINKS

Table of n, a(n) for n=0..27.

FORMULA

a(n) = ~4.5*A057755. - Robert G. Wilson v, Jul 02 2005

EXAMPLE

a(5)=59 because 2^(2^5) + 1 = 4294967297 and the sum of those decimal digits is 59.

MAPLE

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

MATHEMATICA

f[n_] := Plus @@ IntegerDigits[2^(2^n)] + 1; Table[ f[n], {n, 0, 27}] (* Robert G. Wilson v, Jul 02 2005 *)

CROSSREFS

Cf. A000215.

Sequence in context: A078065 A175378 A072655 * A282390 A095290 A080999

Adjacent sequences:  A108298 A108299 A108300 * A108302 A108303 A108304

KEYWORD

base,nonn

AUTHOR

Jason Earls, Jun 29 2005

EXTENSIONS

More terms from Emeric Deutsch and Robert G. Wilson v, Jul 02 2005

STATUS

approved

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Last modified April 10 21:42 EDT 2021. Contains 342856 sequences. (Running on oeis4.)