A071641 a(n) defined by recursion in the formula section.

1, 1, 1, 1, 3, 7, 9, 3, 7, 3, 7, 3, 5, 7, 7, 7, 9, 8, 7, 5, 7, 7, 3, 3, 9, 3, 3, 1, 7, 7, 3, 8, 8, 3, 5, 7, 1, 1, 7, 8, 7, 7, 3, 3, 7, 3, 3, 8, 7, 7, 7, 7, 7, 9, 8, 7, 5, 7, 7, 1, 1, 3, 3, 8, 7, 3, 5, 1, 3, 8, 5, 3, 5, 3, 1, 7, 1, 3, 7, 7, 9, 7, 9, 3, 3, 7, 7, 7, 7, 3, 7, 3, 9, 5, 9, 7, 3, 7, 8, 5, 9, 7, 9, 5, 5

Offset: 0

Author

Roger L. Bagula, Jun 22 2002

Keywords

• nonn
• easy
• less

Comments

All terms are in {1, 3, 5, 7, 8, 9}.

References

• Ivars Peterson, The Jungles of Randomness, 1998, John Wiley and Sons, Inc., page 207.

Crossrefs

Cf. A000040, A072003.

Programs

Mathematica

f[0]=f[1]=f[2]=f[3]=1; f[x_] := f[x]=f[x-1]+f[x-4]+Floor[f[x-1]/10+f[x-4]/10];
g[x_] := g[x]=9-Mod[f[x], 9];
h[x_] := h[x]=10-Mod[Prime[g[x]], 10];
Table[h[n], {n, 0, 200}];

Formula

a(n) = 10 - (prime(g(n)) mod 10) with g(n) = 9 - (f(n) mod 9) and f(n) = f(n-1) + f(n-4) + floor((f(n-1) + f(n-4))/10) for n>= 4, f(n) = 1 for n<4.

Extensions

Edited by Robert G. Wilson v, Jun 25 2002

Edited by the Associate Editors of the OEIS, Jan 28 2022