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A173129 a(n) = cosh(2 * n * arccosh(n)). 9
1, 1, 97, 19601, 7380481, 4517251249, 4097989415521, 5170128475599457, 8661355881006882817, 18605234632923999244961, 49862414878754347585980001, 163104845048002042971670685041, 639582975902942936737758325440001 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Table of n, a(n) for n=0..12.

FORMULA

a(n) = (1/2)*((n+sqrt(n^2-1))^(2*n) + (n-sqrt(n^2-1))^(2*n)). - Artur Jasinski, Feb 14 2010, corrected by Vaclav Kotesovec, Apr 05 2016

MATHEMATICA

Table[Round[Cosh[2 n ArcCosh[n]]], {n, 0, 20}] (* Artur Jasinski *)

Round[Table[1/2 (x - Sqrt[ -1 + x^2])^(2 x) + 1/2 (x + Sqrt[ -1 + x^2])^(2 x), {x, 0, 10}]] (* Artur Jasinski, Feb 14 2010 *)

PROG

(PARI) a(n) = round(cosh(2*n*acosh(n))); \\ Michel Marcus, Apr 05 2016

CROSSREFS

Cf. A058331, A001079, A037270, A071253, A108741, A132592, A146311, A146312, A146313, A173115, A173116, A173121, A173127, A173128.

Sequence in context: A219062 A218318 A233426 * A173354 A176135 A160489

Adjacent sequences:  A173126 A173127 A173128 * A173130 A173131 A173132

KEYWORD

nonn

AUTHOR

Artur Jasinski, Feb 10 2010

STATUS

approved

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Last modified November 24 00:27 EST 2017. Contains 295164 sequences.