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A017054 a(n) = (7*n + 6)^2. 1
36, 169, 400, 729, 1156, 1681, 2304, 3025, 3844, 4761, 5776, 6889, 8100, 9409, 10816, 12321, 13924, 15625, 17424, 19321, 21316, 23409, 25600, 27889, 30276, 32761, 35344, 38025, 40804, 43681, 46656 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

If Y is a fixed 2-subset of a (7n+1)-set X then a(n-1) is the number of 3-subsets of X intersecting Y. - Milan Janjic, Oct 21 2007

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..10000

Milan Janjic, Two Enumerative Functions

Index entries for linear recurrences with constant coefficients, signature (3,-3,1).

FORMULA

a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3); a(0)=36, a(1)=169, a(2)=400. - Harvey P. Dale, Apr 28 2016

MATHEMATICA

(7*Range[0, 30]+6)^2 (* or *) LinearRecurrence[{3, -3, 1}, {36, 169, 400}, 40] (* Harvey P. Dale, Apr 28 2016 *)

PROG

(MAGMA) [(7*n+6)^2: n in [0..40]]; // Vincenzo Librandi, Jul 10 2011

(PARI) a(n)=(7*n+6)^2 \\ Charles R Greathouse IV, Jun 17 2017

CROSSREFS

Cf. A017053 (7*n+6).

Sequence in context: A264474 A338390 A268905 * A231972 A330770 A166708

Adjacent sequences:  A017051 A017052 A017053 * A017055 A017056 A017057

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane

STATUS

approved

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Last modified May 8 20:32 EDT 2021. Contains 343668 sequences. (Running on oeis4.)