A113724 A variant of Golomb's sequence using even numbers: a(n) is the number of times 2*n+2 occurs, starting with a(1) = 2.

2, 4, 4, 6, 6, 6, 6, 8, 8, 8, 8, 10, 10, 10, 10, 10, 10, 12, 12, 12, 12, 12, 12, 14, 14, 14, 14, 14, 14, 16, 16, 16, 16, 16, 16, 18, 18, 18, 18, 18, 18, 18, 18, 20, 20, 20, 20, 20, 20, 20, 20, 22, 22, 22, 22, 22, 22, 22, 22, 24, 24, 24, 24, 24, 24, 24, 24, 26, 26, 26, 26, 26, 26

Offset: 1

Author

Floor van Lamoen and Paul D. Hanna, Nov 08 2005

Keywords

• nonn

Comments

a(n) is taken to be the smallest number >= a(n-1) which is compatible with the description.

Examples

			Start with 2 in row 1 and form a triangle where row n is generated from row n-1 by the rule given in the description. Then row 2 will have (2) 4's, row 3 will have (4) 6's and (4) 8's, etc.
The triangle begins:
2;
4,4;
6,6,6,6,8,8,8,8; ...
The number of terms in each row (also row sums with offset) is given by A113725: [1,2,8,56,984,87848,115679160,...].
		

Crossrefs

Cf. A001462 (Golomb's sequence), A113725, A113722, A113676.

Cf. A080606. [From R. J. Mathar, Aug 13 2008]

Programs

PARI

a=[2,4,4];for(n=2,20, for(i=1,a[n],a=concat(a,2*n+2)));a