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A082176
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Professor E. P. B. Umbugio's sequence.
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3
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0, 0, 206276, 1124101062, 4106026092896, 12565214785548390, 34787981278581970376, 90353184628933414448862, 224610989213093282203310816, 541037084832262355204120965110, 1272999064631803815296028401200376, 2942001006486252167427671506502189262
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OFFSET
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0,3
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COMMENTS
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The problem was to prove that 1946 divides every a(n). The proof uses 2141 - 1770 = 371 = 1863 - 1492 and 2141 - 1863 = 278 = 1770 - 1492, gcd(278,371) = 1, 278*371 = 53*1946 and the fact that x - y not 0 divides x^n - y^n for n>=0. See the Starke reference. The primes that divide every a(n) are 2, 7, 53, 139. Note the historical dates other than 2141 in the formula. This AMM problem was proposed in 1946 (with a reference to April 1).
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REFERENCES
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C. A. Pickover, Die Mathematik und das Goettliche, Spektrum Akademischer Verlag, Heidelberg, Berlin, 1999, pp. 56-8, 398 (English: The Loom of God, Plenum, 1997).
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LINKS
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FORMULA
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a(n) = 1492^n - 1770^n - 1863^n + 2141^n.
a(n) = 7266*a(n-1) - 19690571*a(n-2) + 23585007306*a(n-3) - 10533473613720*a(n-4) for n>3.
G.f: 103138*x^2*(2-3633*x) / ((1-1492*x)*(1-1770*x)*(1-1863*x)*(1-2141*x)).
(End)
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MATHEMATICA
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Table[1492^n - 1770^n - 1863^n + 2141^n, {n, 0, 11}] (* Michael De Vlieger, Nov 21 2015 *)
CoefficientList[Series[103138 x^2 (2-3633 x)/((1-1492 x) (1-1770 x) (1-1863 x) (1-2141 x)), {x, 0, 20}], x] (* Vincenzo Librandi, Nov 22 2015 *)
LinearRecurrence[{7266, -19690571, 23585007306, -10533473613720}, {0, 0, 206276, 1124101062}, 20] (* Harvey P. Dale, Oct 18 2020 *)
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PROG
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(PARI) concat(vector(2), Vec(103138*x^2*(2-3633*x)/((1-1492*x)*(1-1770*x)*(1-1863*x)*(1-2141*x)) + O(x^15))) \\ Colin Barker, Nov 21 2015
(Magma) [1492^n-1770^n-1863^n+2141^n: n in [0..20]]; // Vincenzo Librandi, Nov 22 2015
(SageMath) [1492^n -1770^n -1863^n +2141^n for n in range(31)] # G. C. Greubel, Jan 21 2024
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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