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A133327
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Indices of the 7-gonal numbers that are the sum of 2 consecutive 7-gonal numbers.
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3
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1, 241, 19265, 9435905, 755214769, 369906335809, 29605929343313, 14501068166936753, 1160611641361329697, 568470873910348243537, 45498297535040917426721, 22285195184532403676188961, 1783624258808062403600975185, 873624221055568415003611393825
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OFFSET
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1,2
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COMMENTS
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Also nonnegative integers y in the solution to 10*x^2 - 5*y^2 + 4*x + 3*y + 2 = 0, the corresponding values of x being A133328.
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LINKS
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FORMULA
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The bisections modulo 2 satisfy the same recurrence relation: a(n+2) = 39202*a(n+1) - a(n) - 11760.
G.f.: -x*(17*x^4+8160*x^3-20178*x^2+240*x+1) / ((x-1)*(x^2-198*x+1)*(x^2+198*x+1)). - Colin Barker, Dec 05 2014
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PROG
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(PARI) Vec(-x*(17*x^4+8160*x^3-20178*x^2+240*x+1)/((x-1)*(x^2-198*x+1)*(x^2+198*x+1)) + O(x^100)) \\ Colin Barker, Dec 05 2014
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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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EXTENSIONS
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STATUS
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approved
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