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A016873 a(n) = 5n + 2. 29
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

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

LINKS

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).

FORMULA

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

MAPLE

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

MATHEMATICA

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 *)

PROG

(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

CROSSREFS

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

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane

STATUS

approved

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Last modified August 24 02:32 EDT 2019. Contains 326260 sequences. (Running on oeis4.)