%I A009123
%S A009123 1,0,1,3,8,30,136,693,3968,25260,176896,1351383,11184128,99680490,
%T A009123 951878656,9695756073,104932671488,1202439837720,14544442556416,
%U A009123 185185594118763,2475749026562048,34674437196568950
%V A009123 1,0,1,-3,8,-30,136,-693,3968,-25260,176896,-1351383,11184128,-99680490,
%W A009123 951878656,-9695756073,104932671488,-1202439837720,14544442556416,
%X A009123 -185185594118763,2475749026562048,-34674437196568950
%N A009123 Expansion of cosh(ln(1+sin(x))).
%C A009123 a(2n) = 1/2*A000182(n+1), a(2n+1) = A012007(n+1) = A009567(2n+1)+1.
%C A009123 |a(n)| = number of even alternating permutations on n letters (offset 
               1). - Vladeta Jovovic (vladeta(AT)eunet.rs), May 20 2007
%t A009123 Cosh[ Log[ 1+Sin[ x ] ] ]
%Y A009123 Cf. A000111.
%Y A009123 Sequence in context: A096161 A161779 A074501 this_sequence A066764 A059171 
               A078619
%Y A009123 Adjacent sequences: A009120 A009121 A009122 this_sequence A009124 A009125 
               A009126
%K A009123 sign,easy
%O A009123 0,4
%A A009123 R. H. Hardin (rhhardin(AT)att.net)
%E A009123 Extended with signs Mar 15 1997 by Olivier Gerard.