OFFSET
1,2
LINKS
Ray Chandler, Rows n = 1..322, flattened (first 60 rows from Alois P. Heinz)
Samuel Yates, The Mystique of Repunits, Math. Mag. 51 (1978), 22-28.
EXAMPLE
Triangle begins:
1
11
3 37
101
41 271
7 13
239 4649
73 137
333667
9091
...
MAPLE
with(numtheory):
S:= proc(n) option remember;
`if`(n=1, {1}, S(n-1) union factorset ((10^n-1)/9))
end:
T:= n-> sort([(S(n) minus `if`(n=1, {}, S(n-1)))[]])[]:
seq(T(n), n=1..30); # Alois P. Heinz, Feb 17 2012
MATHEMATICA
S[n_] := S[n] = If[n==1, {1}, S[n-1] ~Union~ FactorInteger[(10^n-1)/9][[ All, 1]]]; T[n_] := Sort[S[n] ~Complement~ If[n==1, {}, S[n-1]]]; Table[ T[n], {n, 1, 30}] // Flatten (* Jean-François Alcover, Mar 13 2017, after Alois P. Heinz *)
CROSSREFS
KEYWORD
nonn,tabf
AUTHOR
N. J. A. Sloane, Jan 19 2012
EXTENSIONS
More terms from Alois P. Heinz, Feb 17 2012
STATUS
approved