a(n) is the first semiprime k such that k-1 and k+1 each have exactly n prime factors (counted with multiplicity).
A365537
a(n) is the first semiprime k such that k-1 and k+1 each have exactly n prime factors (counted with multiplicity).
Terms
- a(0) =4a(1) =34a(2) =51a(3) =55a(4) =1169a(5) =6641a(6) =18751a(7) =204929a(8) =101249a(9) =2490751a(10) =6581249a(11) =68068351a(12) =262986751a(13) =1842131969a(14) =9601957889a(15) =13858918399a(16) =145046192129a(17) =75389157377
External references
- oeis: A365537