Generalized pentagonal numbers: m*(3*m - 1)/2, m = 0, +-1, +-2, +-3, ....

Terms

a(0) =0a(1) =1a(2) =2a(3) =5a(4) =7a(5) =12a(6) =15a(7) =22a(8) =26a(9) =35a(10) =40a(11) =51a(12) =57a(13) =70a(14) =77a(15) =92a(16) =100a(17) =117a(18) =126a(19) =145a(20) =155a(21) =176a(22) =187a(23) =210a(24) =222a(25) =247a(26) =260a(27) =287a(28) =301a(29) =330