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A089043 a(n) = n!^2 + (-1)^n. 1
0, 5, 35, 577, 14399, 518401, 25401599, 1625702401, 131681894399, 13168189440001, 1593350922239999, 229442532802560001, 38775788043632639999, 7600054456551997440001, 1710012252724199423999999, 437763136697395052544000001, 126513546505547170185215999999 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

p = 2*n+1 is prime iff it divides a(n) (Wilson's theorem) for instance let n=5, p =11 : a(5) = 14399 = 11*1309, so 11 is prime.

LINKS

Table of n, a(n) for n=1..17.

FORMULA

a(n) = n^2*(a(n-1)-(-1)^(n-1))+(-1)^n.

EXAMPLE

a(5) = 14399 because 14399=(5!)^2+(-1)^5.

PROG

(PARI) a(n) = n!^2+(-1)^n; \\ Michel Marcus, Oct 02 2016

CROSSREFS

Sequence in context: A034217 A011556 A194927 * A260075 A317816 A034236

Adjacent sequences:  A089040 A089041 A089042 * A089044 A089045 A089046

KEYWORD

easy,nonn

AUTHOR

Serge Boisse (serge.boisse(AT)aviation-civile.gouv.fr), Dec 02 2003

EXTENSIONS

Offset corrected and edited by Michel Marcus, Oct 02 2016

STATUS

approved

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Last modified August 14 17:44 EDT 2018. Contains 313751 sequences. (Running on oeis4.)