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A071355 2*n^2+11*n+12. 3
3, 12, 25, 42, 63, 88, 117, 150, 187, 228, 273, 322, 375, 432, 493, 558, 627, 700, 777, 858, 943, 1032, 1125, 1222, 1323, 1428, 1537, 1650, 1767, 1888, 2013, 2142, 2275, 2412, 2553, 2698, 2847, 3000, 3157, 3318, 3483, 3652, 3825, 4002, 4183, 4368, 4557, 4750, 4947 (list; graph; refs; listen; history; internal format)
OFFSET

-1,1

COMMENTS

If Y is a 3-subset of an 2n-set X then, for n>=3, a(n-3) is the number of (2 n-2)-subsets of X having at least two elements in common with Y. - Milan R. Janjic (agnus(AT)blic.net), Dec 16 2007

LINKS

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

FORMULA

a(n) = (n+4)*(2*n+3). - Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Nov 18 2004

MATHEMATICA

lst={}; Do[AppendTo[lst, 2*n^2+11*n+12], {n, -2, 5!}]; lst...and/or... s=-3; lst={}; Do[s+=n+1; AppendTo[lst, s], {n, 0, 6!, 4}]; lst [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Oct 25 2008]

CROSSREFS

a(n)=A100345(n+4, n-1) for n>0.

Sequence in context: A076506 A009776 A068967 * A199242 A169678 A110859

Adjacent sequences:  A071352 A071353 A071354 * A071356 A071357 A071358

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane (njas(AT)research.att.com), Jun 12 2002

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Last modified February 14 08:24 EST 2012. Contains 205614 sequences.