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First differences of A087128.
2

%I #2 Mar 30 2012 17:37:53

%S 1,3,1,7,9,3,9,3,9,12,3,12,24,9,36,3,33,3,12,9,3,12,9,12,15,24,9,12,

%T 15,33,12,24,3,9,36,3,9,24,36,27,12,12,9,3,21,96,3,9,3,12,9,3,12,105,

%U 3,60,12,9,39,45,27,9,12,3,12,12,45,12,15,33,15,21,3,9,3,12,9,24,3,33,15,9

%N First differences of A087128.

%C It appears that, for n>4, a(n)=3k, for some integer k where k is not equal to 2 (mod 4). This has been verified for more than 3500 terms.

%Y Cf. A087128.

%K nonn

%O 1,2

%A _John W. Layman_, Aug 16 2003