a(n) is the smallest number whose English name has the letter "f" in the n-th position, or -1 if no such number exists.

A164794

a(n) is the smallest number whose English name has the letter "f" in the n-th position, or -1 if no such number exists.

Terms

    a(0) =4a(1) =-1a(2) =15a(3) =-1a(4) =-1a(5) =44a(6) =24a(7) =74a(8) =-1a(9) =-1a(10) =104a(11) =404a(12) =115a(13) =415a(14) =315a(15) =144a(16) =124a(17) =174a(18) =324a(19) =374a(20) =3074a(21) =1104a(22) =1404a(23) =1115a(24) =1415a(25) =1315a(26) =1144a(27) =1124a(28) =1174a(29) =1324

External references