The number of L-shaped corners in all bargraphs of semiperimeter n.

Terms

a(0) =0a(1) =0a(2) =1a(3) =5a(4) =20a(5) =74a(6) =263a(7) =914a(8) =3134a(9) =10655a(10) =36023a(11) =121331a(12) =407610a(13) =1366926a(14) =4578365a(15) =15321750a(16) =51245820a(17) =171335458a(18) =572714527a(19) =1914159445a(20) =6397373996a(21) =21381342737a(22) =71465609723a(23) =238892470728a(24) =798659461590