A113724 - OEIS

%I #9 Mar 02 2015 16:08:50

%S 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,

%T 14,14,14,16,16,16,16,16,16,18,18,18,18,18,18,18,18,20,20,20,20,20,20,

%U 20,20,22,22,22,22,22,22,22,22,24,24,24,24,24,24,24,24,26,26,26,26,26,26

%N 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.

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

%e 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.

%e The triangle begins:

%e 2;

%e 4,4;

%e 6,6,6,6,8,8,8,8; ...

%e The number of terms in each row (also row sums with offset) is given by A113725: [1,2,8,56,984,87848,115679160,...].

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

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

%Y Cf. A080606. [From _R. J. Mathar_, Aug 13 2008]

%K nonn

%O 1,1

%A _Floor van Lamoen_ and _Paul D. Hanna_, Nov 08 2005