a(n) is the smallest tetrahedral number with exactly n prime factors (counted with multiplicity), or -1 if no such number exists.

A358927

a(n) is the smallest tetrahedral number with exactly n prime factors (counted with multiplicity), or -1 if no such number exists.

Terms

    a(0) =1a(1) =-1a(2) =4a(3) =20a(4) =56a(5) =120a(6) =560a(7) =4960a(8) =19600a(9) =41664a(10) =341376a(11) =695520a(12) =7207200a(13) =22238720a(14) =178433024a(15) =1429559296a(16) =179481600a(17) =11453245440a(18) =11444858880a(19) =393079864320

External references