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Search: id:A014601
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| A014601 |
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Congruent to 0 or 3 mod 4. |
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+0
15
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| 0, 3, 4, 7, 8, 11, 12, 15, 16, 19, 20, 23, 24, 27, 28, 31, 32, 35, 36, 39, 40, 43, 44, 47, 48, 51, 52, 55, 56, 59, 60, 63, 64, 67, 68, 71, 72, 75, 76, 79, 80, 83, 84, 87, 88, 91, 92, 95, 96, 99, 100, 103, 104, 107, 108, 111, 112, 115, 116, 119, 120, 123, 124
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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Discriminants of imaginary quadratic fields with D=0,1 mod 4, D<0 (sequence gives -D).
n such that Langford-Skolem problem has a solution - see A014552.
A014494(n) = A000217(a(n)); complement of A042963. - Reinhard Zumkeller (reinhard.zumkeller(AT)lhsystems.com), Oct 04 2004
Also called skew amenable numbers; a number n is skew amenable if there exist a set {a(i)} of integers satisfying the relations n = sum_(1,n) a(i) = -product_(1,n) a(i). Thus we have 8=1+1+1+1+1+1-2+4=-(1*1*1*1*1*1*(-2)*4). - Lekraj Beedassy (blekraj(AT)yahoo.com), Jan 07 2005
A139131(a(n)) = A078636(a(n)). - Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Apr 10 2008
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REFERENCES
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H. Cohen, Course in Computational Alg. No. Theory, Springer, 1993, pp. 514-5.
A. Scholz and B. Schoeneberg, Einfuehrung in die Zahlentheorie, 5. Aufl., de Gruyter, Berlin, New York, 1973, p. 108.
S. F. Barger, Solution to problem 10454, "Amenable Numbers", Amer. Math. Monthly Vol. 105 No. 4 April 1998 MAA Washington DC.
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LINKS
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S. R. Finch, Class number theory
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FORMULA
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a(n) = (n+1)*2 + 1 - n mod 2. - Reinhard Zumkeller (reinhard.zumkeller(AT)lhsystems.com), Apr 21 2003
a(n) = Sum{k=1..n, 2 - (-1)^k} - William A. Tedeschi (fynmun(AT)hotmail.com), Mar 20 2008
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CROSSREFS
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Cf. A079896.
Adjacent sequences: A014598 A014599 A014600 this_sequence A014602 A014603 A014604
Sequence in context: A138971 A032788 A070874 this_sequence A026444 A003171 A028970
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KEYWORD
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nonn,easy
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AUTHOR
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Eric Rains (rains(AT)caltech.edu)
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