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 A062123 a(n) = 2 + 9*n*(1 + n)/2. 10
 2, 11, 29, 56, 92, 137, 191, 254, 326, 407, 497, 596, 704, 821, 947, 1082, 1226, 1379, 1541, 1712, 1892, 2081, 2279, 2486, 2702, 2927, 3161, 3404, 3656, 3917, 4187, 4466, 4754, 5051, 5357, 5672, 5996, 6329, 6671, 7022, 7382, 7751, 8129, 8516, 8912, 9317 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS Third column of A046741. REFERENCES I. P. Goulden and D. M. Jackson, Combinatorial Enumeration, Wiley, N.Y., 1983,(2.3.14). LINKS Harry J. Smith, Table of n, a(n) for n = 0..1000 Index entries for linear recurrences with constant coefficients, signature (3,-3,1). FORMULA G.f.: (1+2*x)*(2+x)/(1-x)^3. Generally, g.f. for k-th column of A046741 is coefficient of y^k in expansion of (1-y)/((1-y-y^2)*(1-y)-(1+y)*x). a(n) = 9*n + a(n-1), with n>0, a(0)=2. - Vincenzo Librandi, Aug 07 2010 E.g.f.: (4 +18*x +9*x^2)*exp(x)/2. - G. C. Greubel, Jan 31 2019 MATHEMATICA Table[2 +9*n*(1+n)/2, {n, 0, 50}] (* G. C. Greubel, Jan 31 2019 *) LinearRecurrence[{3, -3, 1}, {2, 11, 29}, 50] (* Harvey P. Dale, Jan 12 2020 *) PROG (PARI) for (n=0, 1000, write("b062123.txt", n, " ", 2 + (n + n^2)*9/2) ) \\ Harry J. Smith, Aug 02 2009 (MAGMA) [2 +9*n*(1+n)/2: n in [0..50]]; // G. C. Greubel, Jan 31 2019 (Sage) [2 +9*n*(1+n)/2 for n in range(50)] # G. C. Greubel, Jan 31 2019 (GAP) List([0..50], n -> 2 +9*n*(1+n)/2); # G. C. Greubel, Jan 31 2019 CROSSREFS Cf. dumbbells: A002940, A002941, A002889, A046741, A055608, A062124-A062127. Cf. A235332. Sequence in context: A090389 A061238 A046500 * A117560 A024178 A009312 Adjacent sequences:  A062120 A062121 A062122 * A062124 A062125 A062126 KEYWORD nonn,easy AUTHOR Vladeta Jovovic, Jun 04 2001 EXTENSIONS More terms from Larry Reeves (larryr(AT)acm.org), Jun 06 2001 STATUS approved

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Last modified April 11 06:00 EDT 2021. Contains 342886 sequences. (Running on oeis4.)