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A165905 Somos-4 recurrence with a(0)=1, a(1)=2, a(2)=4, a(3)=16 0
1, 2, 4, 16, 48, 224, 1472, 7552, 80384, 782848, 8406016, 170625024, 2540736512, 64470204416, 2076557099008, 55281408770048, 3099925187854336, 147249506912960512, 8547656292050141184, 871531919951033532416 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..19.

FORMULA

a(n)=2^n*A006720(n+1)

PROG

(PARI) a(n)=if(n<4, [1, 2, 4, 16][n+1], (a(n-1)*a(n-3)+a(n-2)^2)/a(n-4))

CROSSREFS

Cf. A006720, A157005, A165904.

Sequence in context: A003433 A153951 A248748 * A104354 A153948 A284730

Adjacent sequences:  A165902 A165903 A165904 * A165906 A165907 A165908

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 21 22:56 EST 2018. Contains 299427 sequences. (Running on oeis4.)