A073820 a(n) = n+1-i such that prime(i)*(n+1-i) is maximized (1 <= i <= n).

1, 2, 3, 2, 3, 2, 3, 4, 5, 4, 5, 6, 7, 5, 6, 7, 8, 9, 8, 9, 10, 10, 11, 12, 13, 10, 11, 12, 13, 14, 15, 16, 15, 16, 17, 17, 18, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 20, 21, 22, 23, 24, 25, 26, 27, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 32, 33, 31, 30, 31, 32, 33, 34

Offset: 1

Author

David Wasserman, Aug 13 2002

Keywords

• easy
• nonn

Comments

3 is the only n for which the maximum is not unique; a(3) could also be given as 2.

Examples

			For n = 5, we take the first 5 primes in ascending order and multiply them by the numbers from 5 to 1 in descending order: 2*5 = 10 3*4 = 12 5*3 = 15 7*2 = 14 11*1 = 11 The largest product is 15, so a(5) = 3.
		

Crossrefs

Cf. A073818, A073819.

Formula

a(n) = A073818(n)/A073819(n).