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A165904 Somos-4 recurrence with a(i)=2^i for 0<=i<=3 1
1, 2, 4, 8, 32, 96, 448, 2944, 15104, 160768, 1565696, 16812032, 341250048, 5081473024, 128940408832, 4153114198016, 110562817540096, 6199850375708672, 294499013825921024, 17095312584100282368, 1743063839902067064832 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..20.

FORMULA

a(n)=2^n*A006720(n)

PROG

(PARI) a(n)=if(n<4, [1, 2, 4, 8][n+1], (a(n-1)*a(n-3)+a(n-2)^2)/a(n-4))

CROSSREFS

Cf. A006720, A157005.

Sequence in context: A194810 A271216 A102000 * A192008 A298989 A074406

Adjacent sequences:  A165901 A165902 A165903 * A165905 A165906 A165907

KEYWORD

nonn

AUTHOR

Jaume Oliver Lafont, Sep 29 2009

EXTENSIONS

"frac" keyword removed. - Jaume Oliver Lafont, Oct 13 2009

STATUS

approved

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Last modified February 20 10:45 EST 2018. Contains 299385 sequences. (Running on oeis4.)