The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A290939 Number of 5-cycles in the n-triangular graph. 3
 0, 0, 24, 312, 1584, 5376, 14448, 33264, 68544, 129888, 230472, 387816, 624624, 969696, 1458912, 2136288, 3055104, 4279104, 5883768, 7957656, 10603824, 13941312, 18106704, 23255760, 29565120, 37234080, 46486440, 57572424, 70770672, 86390304, 104773056, 126295488 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,3 LINKS Eric Weisstein's World of Mathematics, Graph Cycle Eric Weisstein's World of Mathematics, Johnson Graph Eric Weisstein's World of Mathematics, Triangular Graph Index entries for linear recurrences with constant coefficients, signature (7,-21,35,-35,21,-7,1). FORMULA a(n) = 12/5 * binomial(n, 4) * (n^2 + 7*n - 34). a(n) = 7*a(n-1) - 21*a(n-2) + 35*a(n-3) - 35*a(n-4) + 21*a(n-5) - 7*a(n-6) + a(n-7). G.f.: (24 x^2 (-x^2 - 6 x^3 + 4 x^4))/(-1 + x)^7. MATHEMATICA Table[12/5 Binomial[n, 4] (n^2 + 7 n - 34), {n, 2, 20}] LinearRecurrence[{7, -21, 35, -35, 21, -7, 1}, {0, 0, 24, 312, 1584, 5376, 14448}, 20] CoefficientList[Series[(24 (-x^2 - 6 x^3 + 4 x^4))/(-1 + x)^7, {x, 0, 20}], x] PROG (PARI) a(n)=12*binomial(n, 4)*(n^2+7*n-34)/5 \\ Charles R Greathouse IV, Aug 14 2017 CROSSREFS Cf. A002417 (number of 3-cycles in the triangular graph), A151974 (4-cycles), A290940 (6-cycles). Sequence in context: A096821 A168303 A053215 * A004413 A319554 A069779 Adjacent sequences:  A290936 A290937 A290938 * A290940 A290941 A290942 KEYWORD nonn,easy AUTHOR Eric W. Weisstein, Aug 14 2017 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified January 23 20:47 EST 2022. Contains 350515 sequences. (Running on oeis4.)