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 A008851 Congruent to 0 or 1 mod 5. 36
 0, 1, 5, 6, 10, 11, 15, 16, 20, 21, 25, 26, 30, 31, 35, 36, 40, 41, 45, 46, 50, 51, 55, 56, 60, 61, 65, 66, 70, 71, 75, 76, 80, 81, 85, 86, 90, 91, 95, 96, 100, 101, 105, 106, 110, 111, 115, 116, 120, 121, 125, 126, 130, 131, 135, 136, 140, 141, 145, 146, 150, 151 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS n^2 and n have same last digit. REFERENCES Dickson, History of Theory of Numbers, I, p. 459. LINKS Reinhard Zumkeller, Table of n, a(n) for n = 1..10000 Index entries for linear recurrences with constant coefficients, signature (1,1,-1). FORMULA a(n) = 5*n-a(n-1)-4 (with a(0)=0). - Vincenzo Librandi, Nov 18 2010 G.f. x^2*(1+4*x) / ( (1+x)*(x-1)^2 ). - R. J. Mathar, Oct 07 2011 a(n+1) = Sum_k>=0 {A030308(n,k)*A146523(k)}. - Philippe Deléham, Oct 17 2011 a(n) = floor((5/3)*floor(3*(n-1)/2)). - Clark Kimberling, Jul 04 2012 a(n) = (5*n - 13 - 3*(-1)^n)/4. - Robert Israel, Nov 17 2014 MAPLE a[0]:=0:a[1]:=1:for n from 2 to 100 do a[n]:=a[n-2]+5 od: seq(a[n], n=0..61); # Zerinvary Lajos, Mar 16 2008 MATHEMATICA Select[Range[0, 151], MemberQ[{0, 1}, Mod[#, 5]] &] (* T. D. Noe, Mar 31 2013 *) Table[(Abs[Mod[n, 10] - Mod[n^2, 10]]), {n, 1, 100} ] Position[a, 0] (* José de Jesús Camacho Medina, Nov 16 2014 *) PROG (Haskell) a008851 n = a008851_list !! (n-1) a008851_list = [10*n + m | n <- [0..], m <- [0, 1, 5, 6]] -- Reinhard Zumkeller, Jul 27 2011 (PARI) a(n) = 5*(n\2)+bitand(n, 1); /* Joerg Arndt, Mar 31 2013 */ (PARI) a(n) = floor((5/3)*floor(3*(n-1)/2)); /* Joerg Arndt, Mar 31 2013 */ (MAGMA) [n: n in [0..200] | n mod 5 in {0, 1}]; // Vincenzo Librandi, Nov 17 2014 CROSSREFS Cf. A003226, A045953, A046831, A046851, A086457. Sequence in context: A074627 A067612 A064957 * A079259 A275018 A029772 Adjacent sequences:  A008848 A008849 A008850 * A008852 A008853 A008854 KEYWORD nonn,easy AUTHOR EXTENSIONS Offset corrected by Reinhard Zumkeller, Jul 27 2011 STATUS approved

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Last modified October 18 20:08 EDT 2019. Contains 328197 sequences. (Running on oeis4.)