Consider all Pythagorean triples (X,X+7,Z); sequence gives X values.

Terms

a(0) =-3a(1) =0a(2) =5a(3) =8a(4) =21a(5) =48a(6) =65a(7) =140a(8) =297a(9) =396a(10) =833a(11) =1748a(12) =2325a(13) =4872a(14) =10205a(15) =13568a(16) =28413a(17) =59496a(18) =79097a(19) =165620a(20) =346785a(21) =461028a(22) =965321a(23) =2021228a(24) =2687085a(25) =5626320a(26) =11780597a(27) =15661496a(28) =32792613a(29) =68662368