A186194 a(n) = A002275(n) * (A002275(n)+1).
0, 2, 132, 12432, 1235432, 123465432, 12345765432, 1234568765432, 123456798765432, 12345679098765432, 1234567902098765432, 123456790132098765432, 12345679012432098765432, 1234567901235432098765432, 123456790123465432098765432
Offset: 0
Examples
a(1)=1*2=2, a(2)=11*12=132, a(3)=111*112=12432.
Links
- Index entries for linear recurrences with constant coefficients, signature (111,-1110,1000).
Programs
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Mathematica
LinearRecurrence[{111,-1110,1000},{0,2,132},20] (* Harvey P. Dale, Apr 08 2022 *)
Formula
a(n) = 2*A003555(n+1).
n 1's followed by n 8's is b(n)=18,1188,111888,11118888,1111188888, ...; then a(n)=b(n)/9. See its "contrary" A184337(n+1).
G.f.: 2*x*(-1+45*x) / ( (x-1)*(100*x-1)*(10*x-1) ). - R. J. Mathar, Mar 10 2011
Extensions
Zero added by Franklin T. Adams-Watters, Mar 09 2011
Comments