A061501 a(1) = 1, a(n+1) = (a(n) + n) mod 10.

1, 2, 4, 7, 1, 6, 2, 9, 7, 6, 6, 7, 9, 2, 6, 1, 7, 4, 2, 1, 1, 2, 4, 7, 1, 6, 2, 9, 7, 6, 6, 7, 9, 2, 6, 1, 7, 4, 2, 1, 1, 2, 4, 7, 1, 6, 2, 9, 7, 6, 6, 7, 9, 2, 6, 1, 7, 4, 2, 1, 1, 2, 4, 7, 1, 6, 2, 9, 7, 6, 6, 7, 9, 2, 6, 1, 7, 4, 2, 1, 1, 2, 4, 7, 1, 6, 2, 9, 7, 6, 6, 7, 9, 2, 6, 1, 7, 4, 2, 1, 1, 2, 4, 7, 1

Offset: 1

Author

Amarnath Murthy, May 06 2001

Keywords

• base
• nonn
• less

Comments

First row of array shown below.

a(n) = most significant digit of A062273(n).

Period 20: repeat [1, 2, 4, 7, 1, 6, 2, 9, 7, 6, 6, 7, 9, 2, 6, 1, 7, 4, 2, 1]. - Peter M. Chema, Feb 12 2017

Examples

			1 2 4 7 1 6 2 9 7 6 6 ...
3 5 8 2 7 3 0 8 7 7 ...
6 9 3 8 4 1 9 8 8 ...
0 4 9 5 2 0 9 9 ...
5 0 6 3 1 0 0 ...
1 7 4 2 1 1 ...
		

Crossrefs

Cf. A061352, A061353.

Cf. A062273, A077577, A077578.

Cf. A000124.

Programs

Mathematica

a = {1}; Do[AppendTo[a, Mod[a[[n - 1]] + n - 1, 10]], {n, 2, 120}]; a (* Michael De Vlieger, Feb 13 2017 *)

PARI

a(n)=if(n==1,return(1));(a(n-1)+n-1)%10
for(n=1,50,print1(a(n),", ")) \\ Derek Orr, Feb 26 2017

Formula

a(n) = A008954(n-1) + 1.

a(n) = A000124(n) mod 10. - Peter M. Chema, Feb 11 2017

From Chai Wah Wu, Jan 09 2020: (Start)

a(n) = a(n-5) - a(n-10) + a(n-15) for n > 15.

G.f.: x*(-x^14 - 2*x^13 - 4*x^12 - 7*x^11 - x^10 - 5*x^9 - 5*x^7 - 5*x^5 - x^4 - 7*x^3 - 4*x^2 - 2*x - 1)/(x^15 - x^10 + x^5 - 1). (End)

Extensions

Better description and more terms from Larry Reeves (larryr(AT)acm.org), May 08 2001