Sum of even entries in row n of Pascal's triangle.

Terms

a(0) =0a(1) =0a(2) =2a(3) =0a(4) =14a(5) =20a(6) =32a(7) =0a(8) =254a(9) =492a(10) =932a(11) =1584a(12) =3104a(13) =4160a(14) =8192a(15) =0a(16) =65534a(17) =131036a(18) =261836a(19) =521968a(20) =1038884a(21) =2044440a(22) =4029984a(23) =7607296a(24) =15306272a(25) =27305280a(26) =53360192a(27) =77448960a(28) =201334784a(29) =268451840