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Search: id:A033537
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| 0, 7, 18, 33, 52, 75, 102, 133, 168, 207, 250, 297, 348, 403, 462, 525, 592, 663, 738, 817, 900, 987, 1078, 1173, 1272, 1375, 1482, 1593, 1708, 1827, 1950, 2077, 2208, 2343, 2482, 2625, 2772, 2923, 3078
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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Permutations avoiding 12-3 that contain the pattern 32-1 exactly once.
a(n) = A014107(n) + 8*n^2; A100035(a(n)) = 3 for n>1. - Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Oct 31 2004
If Y is a 3-subset of an (2n+1)-set X then, for n>=1, a(n-1) is the number of (2n-1)-subsets of X having at least two elements in common with Y. - Milan R. Janjic (agnus(AT)blic.net), Dec 16 2007
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LINKS
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T. Mansour, Restricted permutations by patterns of type 2-1.
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FORMULA
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a(n)=4*n+a(n-1)-1 (with a(1)=0) [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Nov 08 2009]
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EXAMPLE
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For n=2, a(2)=4*2+0-1=7; n=3, a(3)=4*3+7-1=18; n=4, a(4)=4*4+18-1=33 [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Nov 08 2009]
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MATHEMATICA
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s=0; lst={s}; Do[s+=n++ +7; AppendTo[lst, s], {n, 0, 7!, 4}]; lst [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Nov 16 2008]
s = 0; lst = {s}; Do[s += 2*n + 1; AppendTo[lst, s], {n, 3, 80, 2}]; lst [From Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jul 15 2009]
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CROSSREFS
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Cf. A100036, A100037, A100038, A100039.
Sequence in context: A103572 A049532 A156619 this_sequence A000566 A133673 A023166
Adjacent sequences: A033534 A033535 A033536 this_sequence A033538 A033539 A033540
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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