%I #10 Aug 09 2022 14:18:23
%S 1,2,4,1,4,9,54,47,376,385,3850,3839,46068,46081,645134,645119,
%T 10321904,10321921,185794578,185794559,3715891180,3715891201,
%U 81749606422,81749606399,1961990553576,1961990553601,51011754393626,51011754393599,1428329123020772
%N a(1) = 1; then add 1, multiply by 2, subtract 3, multiply by 4, add 5, multiply by 6, subtract 7, multiply by 8 and so on.
%H Michael S. Branicky, <a href="/A085111/b085111.txt">Table of n, a(n) for n = 1..808</a>
%o (Python)
%o from itertools import count, islice
%o def agen(): # generator of terms
%o an = 1
%o for n in count(1):
%o yield an
%o if n&1: an += (n if n&3 == 1 else -n)
%o else: an *= n
%o print(list(islice(agen(), 30))) # _Michael S. Branicky_, Aug 09 2022
%K nonn
%O 1,2
%A _Amarnath Murthy_, Jul 04 2003
%E More terms from _Ray G. Opao_, Apr 15 2004
%E a(26) and beyond from _Michael S. Branicky_, Aug 09 2022