A120913 Triangle read by rows where t(n,m) is the (ceiling(n/m))th integer from among those positive integers not occurring earlier in the sequence.

1, 3, 2, 6, 5, 4, 10, 8, 9, 7, 15, 13, 12, 14, 11, 21, 18, 17, 19, 20, 16, 28, 25, 24, 23, 26, 27, 22, 36, 32, 31, 30, 33, 34, 35, 29, 45, 41, 39, 40, 38, 42, 43, 44, 37, 55, 50, 49, 48, 47, 51, 52, 53, 54, 46, 66, 61, 59, 58, 60, 57, 62, 63, 64, 65, 56, 78, 72, 70, 69, 71, 68

Offset

1,2

Comments

This is a self-inverse permutation of the positive integers. For fixed n, U(n,k) as defined above is a permution of 1..n. - Franklin T. Adams-Watters, Jul 25 2006

Links

Table of n, a(n) for n=1..72.

Formula

T(n,k) = n(n-1)/2 + U(n,k), where U(n,k) = ceiling(n/k) if ceiling(n/ceiling(n/k)) = k, otherwise U(n,k) = k. - Franklin T. Adams-Watters, Jul 25 2006

Crossrefs

Cf. A120911.

Sequence in context: A194839 A195071 A195081 * A194922 A195080 A194858

Adjacent sequences: A120910 A120911 A120912 * A120914 A120915 A120916

Keyword

easy,nonn,tabl

Author

Leroy Quet, Jul 15 2006

Extensions

More terms from Franklin T. Adams-Watters, Jul 25 2006

Status

approved