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A016873
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a(n) = 5n + 2.
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30
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2, 7, 12, 17, 22, 27, 32, 37, 42, 47, 52, 57, 62, 67, 72, 77, 82, 87, 92, 97, 102, 107, 112, 117, 122, 127, 132, 137, 142, 147, 152, 157, 162, 167, 172, 177, 182, 187, 192, 197, 202, 207, 212, 217, 222, 227, 232, 237, 242, 247, 252, 257, 262, 267, 272, 277
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OFFSET
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0,1
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COMMENTS
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Also solutions to 3^x + 5^x == 1 mod 11. - Cino Hilliard, May 18 2003
Numbers ending in 2 or 7. - Lekraj Beedassy, Jul 08 2006
For n > 2, also the number of (not necessarily maximum) cliques in the n-gear graph. - Eric W. Weisstein, Nov 29 2017
Also, positive integers k such that 10*k+5 is equal to the product of two integers ending with 5. Proof: if 10*k+5 = (10*a+5) * (10*b+5), then k = 10*a*b + 5*(a+b) + 2 = 5 * (a + b + 2*a*b) + 2, of the form 5m + 2. So, 262 is a term because 2625 = 35 * 75. - Bernard Schott, May 15 2019
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LINKS
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Table of n, a(n) for n=0..55.
Cino Hilliard, solutions to 3^x + 5^x == 2 mod 11 [broken link]
Tanya Khovanova, Recursive Sequences
Index entries for linear recurrences with constant coefficients, signature (2,-1).
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FORMULA
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a(n) = 10*n - a(n-1) - 1 (with a(0)=2). - Vincenzo Librandi, Nov 20 2010
G.f.: (2+3*x)/(1-x)^2. - Colin Barker, Jan 08 2012
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MAPLE
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a[1]:=2:for n from 2 to 100 do a[n]:=a[n-1]+5 od: seq(a[n], n=1..47); # Zerinvary Lajos, Mar 16 2008
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MATHEMATICA
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Range[2, 500, 5] (* Vladimir Joseph Stephan Orlovsky, May 26 2011 *)
Table[5 n + 2, {n, 0, 20}] (* Eric W. Weisstein, Nov 29 2017 *)
5 Range[0, 20] + 2 (* Eric W. Weisstein, Nov 29 2017 *)
LinearRecurrence[{2, -1}, {7, 12}, {0, 20}] (* Eric W. Weisstein, Nov 29 2017 *)
CoefficientList[Series[(2 + 3 x)/(-1 + x)^2, {x, 0, 20}], x] (* Eric W. Weisstein, Nov 29 2017 *)
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PROG
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(Sage) [i+2 for i in range(235) if gcd(i, 5) == 5] # Zerinvary Lajos, May 20 2009
(PARI) a(n)=5*n+2 \\ Charles R Greathouse IV, Jul 10 2016
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CROSSREFS
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Cf. A008586, A008587, A016861.
Cf. A053742 (product of two integers ending with 5).
Cf. A324298 (similar with product of two integers ending with 6).
Sequence in context: A045929 A277598 A105501 * A019592 A220120 A131190
Adjacent sequences: A016870 A016871 A016872 * A016874 A016875 A016876
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KEYWORD
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nonn,easy
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AUTHOR
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N. J. A. Sloane
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STATUS
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approved
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