A194732 Units' digits of the nonzero octagonal numbers.

1, 8, 1, 0, 5, 6, 3, 6, 5, 0, 1, 8, 1, 0, 5, 6, 3, 6, 5, 0, 1, 8, 1, 0, 5, 6, 3, 6, 5, 0, 1, 8, 1, 0, 5, 6, 3, 6, 5, 0, 1, 8, 1, 0, 5, 6, 3, 6, 5, 0, 1, 8, 1, 0, 5, 6, 3, 6, 5, 0, 1, 8, 1, 0, 5, 6, 3, 6, 5, 0, 1, 8, 1, 0, 5, 6, 3, 6, 5, 0, 1, 8, 1, 0, 5, 6

Offset

1,2

Comments

This is a periodic sequence with period 10 and cycle 1, 8, 1, 0, 5, 6, 3, 6, 5, 0.

Links

Table of n, a(n) for n=1..86.

Formula

a(n) = a(n-10).

a(n) = 35 -a(n-1) -a(n-2) -a(n-3) -a(n-4) -a(n-5) -a(n-6) -a(n-7) -a(n-8) -a(n-9).

a(n) = (n*(3*n-2)) mod 10.

G.f.: x*(1 +8*x +x^2 +5*x^4 +6*x^5 +3*x^6 +6*x^7 +5*x^8)/((1-x)*(1+x)*(1 +x +x^2 +x^3 +x^4)*(1 -x +x^2 -x^3 +x^4)).

a(n) = A010879(A000567(n)). - Michel Marcus, Aug 10 2015

Example

The seventh nonzero octagonal number is A000567(7)=133, which has units' digit 3. Hence a(7)=3.

Mathematica

Table[Mod[n (3 n - 2), 10], {n, 100}]

Crossrefs

Cf. A000567, A010879.

Sequence in context: A351129 A214097 A357468 * A217739 A110544 A320084

Adjacent sequences: A194729 A194730 A194731 * A194733 A194734 A194735

Keyword

nonn,easy,base

Author

Ant King, Sep 02 2011

Status

approved