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A122206
Number of sequences b with last index n with b(0) = 1, b(i+1) = b(i)+d where d|b(i).
1
1, 1, 2, 5, 17, 66, 307, 1619, 9668, 64112, 469936, 3773496, 32997159, 312542002, 3192352420, 35023164817, 411288004670, 5154265796088, 68746349160704, 973526723323087, 14605620692012861, 231694886107899371
OFFSET
0,3
COMMENTS
b(n) can be as large as 2^n. [From Max Alekseyev, May 10 2009]
EXAMPLE
For n=3, the sequences are 1,2,3,4; 1,2,3,6; 1,2,4,5; 1,2,4,6; and 1,2,4,8. We can't have 1,2,3,5 because the difference (5-3) does not divide 3.
CROSSREFS
Sequence in context: A346506 A362967 A062881 * A104082 A166474 A054769
KEYWORD
nonn
AUTHOR
EXTENSIONS
a(15)..a(21) from Max Alekseyev, May 10 2009
STATUS
approved