Third differences of seventh powers (A001015).

Terms

a(0) =1a(1) =125a(2) =1806a(3) =10206a(4) =35406a(5) =92526a(6) =201726a(7) =388206a(8) =682206a(9) =1119006a(10) =1738926a(11) =2587326a(12) =3714606a(13) =5176206a(14) =7032606a(15) =9349326a(16) =12196926a(17) =15651006a(18) =19792206a(19) =24706206a(20) =30483726a(21) =37220526a(22) =45017406a(23) =53980206a(24) =64219806a(25) =75852126a(26) =88998126a(27) =103783806a(28) =120340206