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A002130
Generalized sum of divisors function.
(Formerly M2238 N0888)
2
1, -1, 1, 3, -2, 1, -5, 23, -25, 27, -49, 74, -62, 85, -132, 165, -195, 229, -240, 325, -374, 379, -469, 553, -590, 746, -805, 854, -1000, 1085, -1168, 1284, -1396, 1668, -1767, 1815, -2030, 2297, -2450, 2480, -2849, 3293, -3113, 3278, -3772, 4091, -4230, 4213, -4830, 5607, -5499, 5430, -6018, 6922, -6880
OFFSET
3,4
REFERENCES
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
LINKS
P. A. MacMahon, Divisors of numbers and their continuations in the theory of partitions, Proc. London Math. Soc., 19 (1919), 75-113; Coll. Papers II, pp. 303-341.
FORMULA
G.f.: (t(1)^2-t(2))/2 where t(i) = Sum_{n>=1} x^(n*i)/(1+x^n)^(2*i), i=1..2. - Vladeta Jovovic, Sep 21 2007
MATHEMATICA
terms = 55; offset = 3; t[i_] := Sum[x^(n*i)/(1 + x^n)^(2*i), {n, 1, terms + 5}]; s = Series[(t[1]^2 - t[2])/2, {x, 0, terms + 5 }]; A002130 = CoefficientList[s, x][[offset + 1 ;; terms + offset]] (* Jean-François Alcover, Dec 11 2014, after Vladeta Jovovic *)
CROSSREFS
A diagonal of A060044.
Sequence in context: A144252 A248033 A318254 * A089145 A324644 A364256
KEYWORD
sign,easy
EXTENSIONS
More terms from Naohiro Nomoto, Jan 24 2002
More terms from Vladeta Jovovic, Sep 21 2007
STATUS
approved