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A198411 a(n)= (4^(2^n) + 2^(2^n) + 1)/7. 0
1, 3, 39, 9399, 613576119, 2635249154000645559, 48611766702991209068831621643639680439, 16541727033902313631938712144098272550515752433223071786131565516477842550199 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Let b(n) = 4^(2^n) + 2^(2^n) + 1, then b(n+1) = b(n)^2 - 2(8^(2^n) + 4^(2^n)+ 2^(2^n) ) == 1 + 4^(2^n)+ 2^(2^n)= b(n) == 0 (mod 7).

LINKS

Table of n, a(n) for n=0..7.

EXAMPLE

a(2) = (4^(2^2) + 2^(2^2) + 1)/7 = 273/7 = 39.

MAPLE

for n from 0 to 9 do:x:=  (4^(2^n) + 2^(2^n) + 1)/7

:  printf(`%d, `, x):od:

CROSSREFS

Sequence in context: A188410 A188388 A076628 * A097421 A180418 A166999

Adjacent sequences:  A198408 A198409 A198410 * A198412 A198413 A198414

KEYWORD

nonn

AUTHOR

Michel Lagneau, Oct 24 2011

STATUS

approved

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Last modified October 18 04:46 EDT 2019. Contains 328145 sequences. (Running on oeis4.)