A306185 - OEIS

%I #13 Oct 26 2024 21:17:49

%S 5,23,153,1329,14235,181215,2672145,44781345,840523635,17465201775,

%T 397983749625,9867844134225,264469801070475,7618612476650175,

%U 234748657653134625,7703855828862818625,268263758052098683875,9879138385352252391375,383608053176023482431625,15664153113813817068080625

%N a(n) = (2n+1)!! + (2n)!! where k!! = A006882(k).

%F a(n) = A006882(2*n+1) + A006882(2*n).

%e a(3) = A006882(7) + A006882(6) = (7*5*3) + (6*4*2) = 105 + 48 = 153.

%o (Python)

%o o=e=1

%o for n in range(2, 99, 2):

%o   o*=n+1

%o   e*=n

%o   print(o+e, end=', ')

%Y Cf. A006882, A122649, A129890, A232617, A232618, A306184.

%K nonn

%O 1,1

%A _Alex Ratushnyak_, Jan 27 2019