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A178248
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a(n) = 12^n + 1.
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22
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2, 13, 145, 1729, 20737, 248833, 2985985, 35831809, 429981697, 5159780353, 61917364225, 743008370689, 8916100448257, 106993205379073, 1283918464548865, 15407021574586369, 184884258895036417, 2218611106740436993
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OFFSET
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0,1
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COMMENTS
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Prime factors of a(n) are in the Cunningham Project.
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LINKS
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FORMULA
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O.g.f.: (2-13*x)/(1-13*x+12*x^2) = (2-13*x)/((1-x)(1-12*x)).
a(n) = 12*a(n-1) - 11 for n>0.
a(n) = 13*a(n-1) - 12*a(n-2) for n>1.
a(n) = (11*A016125(n) + 13)/12. (End)
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EXAMPLE
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a(3) = 12^3 + 1 = 1729.
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MATHEMATICA
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nmax = 17; 12^Range[0, nmax] + 1
LinearRecurrence[{13, -12}, {2, 13}, 20] (* Harvey P. Dale, Nov 02 2015 *)
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PROG
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CROSSREFS
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Cf. A000051, A001021, A007689, A016125, A024140, A034472, A034474, A034491, A034524, A052539, A062394, A062395, A062396, A062397, A063376, A063481, A074600-A074624, A228081.
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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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