Triangle of coefficients in expansion of (1+7x)^n.

Terms

a(0) =1a(1) =1a(2) =7a(3) =1a(4) =14a(5) =49a(6) =1a(7) =21a(8) =147a(9) =343a(10) =1a(11) =28a(12) =294a(13) =1372a(14) =2401a(15) =1a(16) =35a(17) =490a(18) =3430a(19) =12005a(20) =16807a(21) =1a(22) =42a(23) =735a(24) =6860a(25) =36015a(26) =100842a(27) =117649a(28) =1a(29) =49