Number of strings of numbers x(i=1..4) in 0..n with sum i*x(i) equal to n*4.

Terms

a(0) =2a(1) =7a(2) =14a(3) =28a(4) =46a(5) =74a(6) =107a(7) =154a(8) =208a(9) =278a(10) =357a(11) =456a(12) =565a(13) =697a(14) =841a(15) =1011a(16) =1195a(17) =1408a(18) =1636a(19) =1897a(20) =2175a(21) =2488a(22) =2820a(23) =3191a(24) =3582a(25) =4015a(26) =4470a(27) =4970a(28) =5494a(29) =6066