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Search: id:A063488
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| 1, 6, 20, 49, 99, 176, 286, 435, 629, 874, 1176, 1541, 1975, 2484, 3074, 3751, 4521, 5390, 6364, 7449, 8651, 9976, 11430, 13019, 14749, 16626, 18656, 20845, 23199, 25724, 28426, 31311, 34385, 37654, 41124, 44801, 48691, 52800, 57134
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OFFSET
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1,2
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COMMENT
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Sum of two consecutive terms of A006003(n) = n(n^2+1)/2. a(n) = A006003(n-1) + A006003(n). - Alexander Adamchuk (alex(AT)kolmogorov.com), Jun 03 2006
If a 2-set Y and a 3-set Z are disjoint subsets of an n-set X then a(n-4) is the number of 5-subsets of X intersecting both Y and Z. - Milan R. Janjic (agnus(AT)blic.net), Sep 08 2007
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REFERENCES
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T. P. Martin, Shells of atoms, Phys. Reports, 273 (1996), 199-241, eq. (10).
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LINKS
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Harry J. Smith, Table of n, a(n) for n=1,...,1000
Milan Janjic, Two Enumerative Functions
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FORMULA
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G.f.: (1+x)*(1+x+x^2)/(1-x)^4 [From Jaume Oliver Lafont (joliverlafont(AT)gmail.com), Aug 30 2009]
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PROGRAM
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(PARI) { for (n=1, 1000, write("b063488.txt", n, " ", (2*n - 1)*(n^2 - n + 2)/2) ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Aug 23 2009]
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CROSSREFS
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1/12*t*(2*n^3-3*n^2+n)+2*n-1 for t = 2, 4, 6, ... gives A049480, A005894, A063488, A001845, A063489, A005898, A063490, A057813, A063491, A005902, A063492, A005917, A063493, A063494, A063495, A063496.
Cf. A006003.
Sequence in context: A011928 A055455 A050768 this_sequence A002415 A052515 A067117
Adjacent sequences: A063485 A063486 A063487 this_sequence A063489 A063490 A063491
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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), Aug 01 2001
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