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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

N. J. A. Sloane.

EXTENSIONS

Offset corrected by Reinhard Zumkeller, Jul 27 2011

STATUS

approved

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Last modified December 5 17:42 EST 2019. Contains 329768 sequences. (Running on oeis4.)