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

0,5

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.

Links

Table of n, a(n) for n=0..104.

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.

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}];

Crossrefs

Cf. A000040, A072003.

Sequence in context: A197682 A021729 A198236 * A093336 A038135 A087655

Adjacent sequences: A071638 A071639 A071640 * A071642 A071643 A071644

Keyword

nonn,easy,less

Author

Roger L. Bagula, Jun 22 2002

Extensions

Edited by Robert G. Wilson v, Jun 25 2002

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

Status

approved