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A177019
a(n) = 3*10^(2*n) + 3*10^n + 1.
2
7, 331, 30301, 3003001, 300030001, 30000300001, 3000003000001, 300000030000001, 30000000300000001, 3000000003000000001, 300000000030000000001, 30000000000300000000001, 3000000000003000000000001, 300000000000030000000000001, 30000000000000300000000000001, 3000000000000003000000000000001
OFFSET
0,1
FORMULA
G.f.: (7-446*x+1330*x^2)/((1-x)*(1-10*x)*(1-100*x)). - Vincenzo Librandi, Aug 19 2014
E.g.f.: exp(x)*(1 + 3*exp(9*x) + 3*exp(99*x)). - Stefano Spezia, Aug 05 2024
EXAMPLE
For n=0, a(0)=7; n=1, a(1)=3*10^2+3*10+1=331.
MATHEMATICA
CoefficientList[Series[(7 - 446 x + 1330 x^2)/((1 - x)(1 - 10 x) (1 - 100 x)), {x, 0, 20}], x] (* Vincenzo Librandi, Aug 19 2014 *)
PROG
(Magma) [(3*10^(2*n)+3*10^n+1): n in [0..15]];
CROSSREFS
Sequence in context: A374418 A092588 A049686 * A160432 A324233 A009587
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, May 24 2010
STATUS
approved