Odd pentagonal numbers.

Terms

a(0) =1a(1) =5a(2) =35a(3) =51a(4) =117a(5) =145a(6) =247a(7) =287a(8) =425a(9) =477a(10) =651a(11) =715a(12) =925a(13) =1001a(14) =1247a(15) =1335a(16) =1617a(17) =1717a(18) =2035a(19) =2147a(20) =2501a(21) =2625a(22) =3015a(23) =3151a(24) =3577a(25) =3725a(26) =4187a(27) =4347a(28) =4845a(29) =5017