OFFSET
1,3
COMMENTS
The smallest non-computable number here is 195. The largest computable number here is 9^9 = 387420489.
LINKS
Alois P. Heinz, Table of n, a(n) for n = 1..4769
MAPLE
f:= proc(n) f(n):= `if`(n=1, {9}, {seq(seq(seq([x+y, x-y, x*y,
`if`(y=0, [][], x/y)][], y=f(n-j)), x=f(j)), j=1..n-1)})
end:
sort([select(z->z>=0 and is(z, integer), f(9))[]])[];
PROG
(PARI) A258070(n=9, S=Vec([[n]], n))={for(n=2, n, S[n]=Set(concat(vector(n\2, k, Set(concat([Set(concat([[T+U, T-U, U-T, if(U, T/U), if(T, U/T), T*U] | T <- S[n-k]])) | U <- S[k]])))))); select(t->t>=0 && type(t)=="t_INT", S[n])} \\ Requires at least 30 MB stack. (Use allocatemem()). A258070() yields this sequence, use optional arg to compute variants. - M. F. Hasler, Nov 26 2018
CROSSREFS
KEYWORD
nonn,fini,full
AUTHOR
Alois P. Heinz, May 18 2015
STATUS
approved