25-gonal pyramidal numbers: a(n) = n*(n+1)*(23*n-20)/6.

Terms

a(0) =0a(1) =1a(2) =26a(3) =98a(4) =240a(5) =475a(6) =826a(7) =1316a(8) =1968a(9) =2805a(10) =3850a(11) =5126a(12) =6656a(13) =8463a(14) =10570a(15) =13000a(16) =15776a(17) =18921a(18) =22458a(19) =26410a(20) =30800a(21) =35651a(22) =40986a(23) =46828a(24) =53200a(25) =60125a(26) =67626a(27) =75726a(28) =84448a(29) =93815