a(n) is the index of the smallest triangular number containing exactly n 5's.
A048360
a(n) is the index of the smallest triangular number containing exactly n 5's.
Terms
- a(0) =5a(1) =10a(2) =105a(3) =714a(4) =5010a(5) =34221a(6) =103494a(7) =317885a(8) =3243010a(9) =1054130a(10) =55708989a(11) =280555005a(12) =1051237885a(13) =5206833885a(14) =30184681729a(15) =105409283410
External references
- oeis: A048360