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A091628
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Concatenation of n 2's followed by 3.
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6
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23, 223, 2223, 22223, 222223, 2222223, 22222223, 222222223, 2222222223, 22222222223, 222222222223, 2222222222223, 22222222222223, 222222222222223, 2222222222222223, 22222222222222223, 222222222222222223
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OFFSET
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1,1
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COMMENTS
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Sequence arising in Farideh Firoozbakht's solution to Prime Puzzle 251; 23 is the only pointer prime (A089823) not containing the digit "1".
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LINKS
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FORMULA
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a(n) = (10^(n+1) - 1)/9*2 + 1.
a(n) = 11*a(n-1) - 10*a(n-2).
G.f.: x*(23-30*x)/((1-x)*(1-10*x)). (End)
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PROG
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(Magma) [ n eq 1 select 23 else 10*Self(n-1)-7: n in [1..17] ];
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CROSSREFS
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KEYWORD
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base,easy,nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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