A077341 Triangle in which n-th row contains the first n numbers, not already present, that begin with n.

1, 2, 20, 3, 30, 31, 4, 40, 41, 42, 5, 50, 51, 52, 53, 6, 60, 61, 62, 63, 64, 7, 70, 71, 72, 73, 74, 75, 8, 80, 81, 82, 83, 84, 85, 86, 9, 90, 91, 92, 93, 94, 95, 96, 97, 10, 100, 101, 102, 103, 104, 105, 106, 107, 108, 11, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 12

Offset: 1

Author

Amarnath Murthy, Nov 05 2002

Keywords

• base
• easy
• nonn
• tabl

Comments

Every positive number appears exactly once. Proof: N will appear as the first term of row N, unless it has already appeared. And no term is repeated, by definition.

The first term of the 20th row is 200 unlike the 20th row of A077339 where it is 20.

Examples

			Triangle begins:
1
2 20
3 30 31
4 40 41 42
5 50 51 52 53
...
		

Links

• M. F. Hasler, Table of n, a(n) for n = 1..5350

Crossrefs

Cf. A077339, A077340 (see there for differences), A077342, A077343.

Programs

PARI

{u=[];for(m=1,19,o=0;for(n=1,m,while(setsearch(u,a=A077339(m,n+o)),o++);u=setunion(u,Set(a));print1(a",")))} \\ M. F. Hasler, Jan 08 2013

Extensions

Edited by N. J. A. Sloane, Jun 12 2007