a(n) = largest prime in the factorization of n-th Franel number (A000172).

Terms

a(0) =2a(1) =5a(2) =7a(3) =173a(4) =563a(5) =73a(6) =41a(7) =369581a(8) =1409a(9) =109a(10) =449a(11) =176459a(12) =44221a(13) =12148537a(14) =148381a(15) =11399977a(16) =5779337237a(17) =151431487a(18) =26013917a(19) =57405011a(20) =939783003793a(21) =277157a(22) =191141a(23) =13515438731a(24) =79702499a(25) =236463558839a(27) =313527009031