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A054567
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4*n^2 - 7*n + 4.
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10
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1, 6, 19, 40, 69, 106, 151, 204, 265, 334, 411, 496, 589, 690, 799, 916, 1041, 1174, 1315, 1464, 1621, 1786, 1959, 2140, 2329, 2526, 2731, 2944, 3165, 3394, 3631, 3876, 4129, 4390, 4659, 4936, 5221, 5514, 5815, 6124, 6441, 6766, 7099, 7440, 7789, 8146
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| The number 1 is placed in the middle of a sheet of squared paper and the numbers 2, 3, 4, 5, 6, etc. are written in a clockwise spiral around 1, as in A068225 etc. This sequence is read off along one of the rays from 1.
Ulam's spiral (W spoke). - Robert G. Wilson v, Oct 31 2011
a(n) = A204674(n-1) / n. [Reinhard Zumkeller, Jan 18 2012]
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FORMULA
| a(n)=8*n+a(n-1)-11 (with a(1)=1) [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Aug 07 2010]
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EXAMPLE
| For n=2, a(2)=8*2+1-11=6; n=3, a(3)=8*3+6-11=19; n=4, a(4)=8*4+19-11=40 [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Aug 07 2010]
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MATHEMATICA
| Table[4*n^2-7*n+4, {n, 100}] [From Vladimir Orlovsky, Sep 01 2008]
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CROSSREFS
| Cf. A054566, A068225, A054552, A054554, A054556, A054569, A033951.
Sequence in context: A090381 A106398 A179986 * A096957 A173980 A035495
Adjacent sequences: A054564 A054565 A054566 * A054568 A054569 A054570
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KEYWORD
| easy,nonn
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AUTHOR
| Enoch Haga, G. L. Honaker, Jr. (Enokh(AT)comcast.net), Apr 10 2000
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EXTENSIONS
| Edited by Frank Ellermann, Feb 24 2002
Typo fixed by Charles R Greathouse IV (charles.greathouse(AT)case.edu), Oct 28 2009
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