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A062123
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2 + (n + n^2)*9/2.
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9
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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; internal format)
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OFFSET
| 0,1
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COMMENTS
| Third column of A046741.
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REFERENCES
| I. P. Goulden and D. M. Jackson, Combinatorial Enumeration, Wiley, N.Y., 1983,(2.3.14).
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LINKS
| Harry J. Smith, Table of n, a(n) for n=0..1000
Index entries for sequences related to linear recurrences with constant coefficients, signature (3,-3,1).
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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 a(0)=2) [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Aug 07 2010]
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EXAMPLE
| a(1)=9*1+2=11; a(2)=9*2+11=29; a(3)=9*3+29=56 [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Aug 07 2010]
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PROG
| (PARI) { for (n=0, 1000, write("b062123.txt", n, " ", 2 + (n + n^2)*9/2) ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Aug 02 2009]
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CROSSREFS
| Cf. dumbbells: A002940, A002941, A002889, A046741, A055608, A062124-A062127.
Sequence in context: A090389 A061238 A046500 * A117560 A024178 A009312
Adjacent sequences: A062120 A062121 A062122 * A062124 A062125 A062126
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KEYWORD
| easy,nonn
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AUTHOR
| Vladeta Jovovic (vladeta(AT)eunet.rs), Jun 04 2001
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EXTENSIONS
| More terms from Larry Reeves (larryr(AT)acm.org), Jun 06 2001
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