a(1) = 4, a(n) = concatenation of two closest factors of a(n-1) whose product equals a(n-1) or if a(n-1) is a prime then the concatenation of 1 and a(n-1).
A063380
a(1) = 4, a(n) = concatenation of two closest factors of a(n-1) whose product equals a(n-1) or if a(n-1) is a prime then the concatenation of 1 and a(n-1).
Terms
- a(0) =4a(1) =22a(2) =211a(3) =1211a(4) =7173a(5) =9797a(6) =97101a(7) =910789a(8) =1182799a(9) =1319029a(10) =6719687a(11) =7678761a(12) =32559587a(13) =257126691a(14) =1591617149a(15) =6653239233a(16) =62767105999a(17) =126149775659a(18) =432933715713
External references
- oeis: A063380