A072845 Let S(1) = {1, 3, 7, 9}, S(n) be obtained from S(n-1) via 1 -> {1, 3, 7, 9}, 3 -> {3, 9, 1, 7}, 7 -> {7, 1, 9, 3}, 9 -> {9, 7, 3, 1}, then this sequence is the concatenation of S(1), S(2), ...

1, 3, 7, 9, 1, 3, 7, 9, 3, 9, 1, 7, 7, 1, 9, 3, 9, 7, 3, 1, 1, 3, 7, 9, 3, 9, 1, 7, 7, 1, 9, 3, 9, 7, 3, 1, 3, 9, 1, 7, 9, 7, 3, 1, 1, 3, 7, 9, 7, 1, 9, 3, 7, 1, 9, 3, 1, 3, 7, 9, 9, 7, 3, 1, 3, 9, 1, 7, 9, 7, 3, 1, 7, 1, 9, 3, 3, 9, 1, 7, 1, 3, 7, 9, 1, 3, 7, 9, 3, 9, 1, 7, 7, 1, 9, 3, 9, 7, 3, 1, 3, 9, 1, 7, 9

Offset

1,2

Links

Table of n, a(n) for n=1..105.

Maple

S[1]:= [1, 3, 7, 9]:
R:= [1=(1, 3, 7, 9), 3 = (3, 9, 1, 7), 7 = (7, 1, 9, 3), 9 = (9, 7, 3, 1)]:
for i from 1 to 4 do S[i+1]:= subs(R, S[i]) od:
seq(op(S[i]), i=1..5); # Robert Israel, Dec 25 2022

Mathematica

ar={1, 3, 7, 9};
f[x_]=Mod[ar*x, 10];
br=Flatten[ NestList[f, ar, 3]]

Prog

(PARI) lista(nn) = {my(m = [1, 3, 7, 9], v = m); for (i=1, nn, my(w = []); for (j=1, 4, for (k=1, #v, w = concat(w, m[j]*v[k] % 10); ); ); v = w; ); w; }
lista(3) \\ Michel Marcus, Jul 01 2019

Crossrefs

Sequence in context: A336045 A090458 A131712 * A197481 A197682 A021729

Adjacent sequences: A072842 A072843 A072844 * A072846 A072847 A072848

Keyword

nonn,less

Author

Roger L. Bagula, Jul 24 2002

Extensions

Edited by Robert G. Wilson v, Jul 27 2002

Edited with name from Jianing Song by Sean A. Irvine, Mar 25 2026

Status

approved