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Search: id:A042948
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| A042948 |
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Congruent to 0 or 1 mod 4. |
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+0
15
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| 0, 1, 4, 5, 8, 9, 12, 13, 16, 17, 20, 21, 24, 25, 28, 29, 32, 33, 36, 37, 40, 41, 44, 45, 48, 49, 52, 53, 56, 57, 60, 61, 64, 65, 68, 69, 72, 73, 76, 77, 80, 81, 84, 85, 88, 89, 92, 93, 96, 97, 100, 101, 104, 105, 108
(list; graph; listen)
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OFFSET
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0,3
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COMMENT
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Maximum number of squares attacked by a bishop on an n X n chessboard - Stewart Gordon (smjg(AT)iname.com), Mar 23 2001
Also number of squares attacked by a bishop on a toroidal chessboard. - Diego Torres (torresvillarroel(AT)hotmail.com), May 30 2001
Numbers n such that {1,2,3,...,n-1,n} is a perfect Skolem set. - Emeric Deutsch (deutsch(AT)duke.poly.edu), Nov 24 2006
The number of terms which lie on the principal diagonals of an n X n square spiral. - William A. Tedeschi (fynmun(AT)hotmail.com), Mar 02 2008
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REFERENCES
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T. Skolem, On certain distributions of integers in pairs with given differences, Math. Scand., 1957, vol. 5, 57-68.
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FORMULA
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G.f.: (x+3*x^2)/((1-x)*(1-x^2)). a(n)=a(n-1)+2+(-1)^n - Michael Somos, Jan 12 2000.
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MAPLE
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a[0]:=0:a[1]:=1:for n from 2 to 100 do a[n]:=a[n-2]+4 od: seq(a[n], n=0..54); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Mar 16 2008
seq(add(irem(3^k, 4), k=4..n), n=3..57); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Apr 20 2008
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PROGRAM
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(PARI) a(n)=2*n-n%2
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CROSSREFS
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A042948(n) = A042963(n)-1.
Adjacent sequences: A042945 A042946 A042947 this_sequence A042949 A042950 A042951
Sequence in context: A104883 A042956 A128217 this_sequence A126001 A073320 A020668
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KEYWORD
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nonn
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AUTHOR
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njas
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