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Search: id:A022268
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| 0, 5, 21, 48, 86, 135, 195, 266, 348, 441, 545, 660, 786, 923, 1071, 1230, 1400, 1581, 1773, 1976, 2190, 2415, 2651, 2898, 3156, 3425, 3705, 3996, 4298, 4611, 4935, 5270, 5616, 5973, 6341, 6720, 7110
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OFFSET
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0,2
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COMMENT
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Number of sets with two elements which can be obtained by selecting unique elements from two sets with 2n and 3n elements respectively and n common elements. - Polina S. Dolmatova (polinasport(AT)mail.ru), Jul 11 2003
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FORMULA
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a(n)=11*n+a(n-1)-17 (with a(1)=0) [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Nov 12 2009]
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EXAMPLE
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For n=2, a(2)=11*2+0-17=5, n=3, a(3)=11*3+5-17=21; n=4, a(4)=11*4+21-17=48 [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Nov 12 2009]
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MATHEMATICA
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s=0; lst={s}; Do[s+=n++ +5; AppendTo[lst, s], {n, 0, 7!, 11}]; lst [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Nov 16 2008]
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CROSSREFS
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Sequence in context: A166010 A146846 A041825 this_sequence A146721 A099979 A039659
Adjacent sequences: A022265 A022266 A022267 this_sequence A022269 A022270 A022271
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KEYWORD
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nonn,new
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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