A060352 a(n) = n*3^n - 1.
2, 17, 80, 323, 1214, 4373, 15308, 52487, 177146, 590489, 1948616, 6377291, 20726198, 66961565, 215233604, 688747535, 2195382770, 6973568801, 22082967872, 69735688019, 219667417262, 690383311397, 2165293113020, 6778308875543, 21182215236074, 66088511536553, 205891132094648
Offset: 1
Links
- Harry J. Smith, Table of n, a(n) for n = 1..200
- Paul Leyland, Factors of Cullen and Woodall numbers
- Paul Leyland, Generalized Cullen and Woodall numbers
- Amelia Carolina Sparavigna, The groupoids of Mersenne, Fermat, Cullen, Woodall and other Numbers and their representations by means of integer sequences, Politecnico di Torino, Italy (2019), [math.NT].
- Amelia Carolina Sparavigna, Some Groupoids and their Representations by Means of Integer Sequences, International Journal of Sciences (2019) Vol. 8, No. 10.
- Index entries for linear recurrences with constant coefficients, signature (7,-15,9).
Crossrefs
Cf. A060353.
Programs
-
Mathematica
Table[n*3^n-1,{n,50}] (* Vladimir Joseph Stephan Orlovsky, May 19 2011 *) LinearRecurrence[{7,-15,9},{2,17,80},50] (* Harvey P. Dale, Dec 14 2012 *) -
PARI
a(n) = { n*3^n - 1 } \\ Harry J. Smith, Jul 04 2009
Formula
G.f.: x*(2-3*x)*(1+3*x)/((1-x)*(1-3*x)^2). - Colin Barker, Apr 22 2012
a(n) = 7*a(n-1) - 15*a(n-2) + 9*a(n-3), a(1)=2, a(2)=17, a(3)=80. - Harvey P. Dale, Dec 14 2012
E.g.f.: 1 + exp(x)*(3*exp(2*x)*x - 1). - Stefano Spezia, Jan 05 2020