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A107583
a(n) = 3^n - 3*n.
11
1, 0, 3, 18, 69, 228, 711, 2166, 6537, 19656, 59019, 177114, 531405, 1594284, 4782927, 14348862, 43046673, 129140112, 387420435, 1162261410, 3486784341, 10460353140, 31381059543, 94143178758, 282429536409, 847288609368, 2541865828251, 7625597484906, 22876792454877
OFFSET
0,3
COMMENTS
a(n) is the number k such that the number m with n 3's and k 1's has digit product = digit sum = 3^n.
FORMULA
From Elmo R. Oliveira, Sep 09 2024: (Start)
G.f.: (1 - 5*x + 10*x^2)/((1 - 3*x)*(1 - x)^2).
E.g.f.: exp(x)*(exp(2*x) - 3*x).
a(n) = 5*a(n-1) - 7*a(n-2) + 3*a(n-3) for n > 2. (End)
EXAMPLE
Corresponding numbers m are 1, 3, 11133, 111111111111111111333, ...
MATHEMATICA
Table[3^m-3*m, {m, 0, 20}]
PROG
(Magma) [3^n-3*n: n in [0..30]]; // Vincenzo Librandi, Oct 22 2011
(PARI) a(n)=3^n-3*n \\ Charles R Greathouse IV, Sep 08 2012
CROSSREFS
Sequence in context: A026576 A048899 A337142 * A373651 A157535 A373065
KEYWORD
nonn,easy
AUTHOR
Zak Seidov, May 16 2005
EXTENSIONS
Corrected by Charles R Greathouse IV, Sep 08 2012
STATUS
approved