A214803 Frobenius numbers of numerators and denominators of rational numbers in order of their canonical enumeration.

-1, -1, 1, -1, 5, -1, 3, 7, 11, -1, 19, -1, 5, 11, 17, 23, 29, -1, 13, 27, 41, -1, 7, 23, 31, 47, 55, -1, 17, 53, 71, -1, 9, 19, 29, 39, 49, 59, 69, 79, 89, -1, 43, 65, 109, -1, 11, 23, 35, 47, 59, 71, 83, 95, 107, 119, 131, -1, 25, 51, 103, 129, 155, -1, 13

Offset: 1

Author

Reinhard Zumkeller, Jul 29 2012

Keywords

• sign

Comments

a(n) = A020652(n) * A038567(n) - A020652(n) - A038567(n);

for n > 1: a(A015614(n)) = A165900(n-1);

a(A002088(n)) = -1.

Links

• Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
• Eric Weisstein's World of Mathematics, Frobenius Number.
• Wikipedia, Coin problem

Programs

Haskell

a214803 n = a214803_list !! (n-1)
a214803_list = [x * y - x - y | y <- [1..], x <- [1..y-1], gcd x y == 1]