OFFSET
0,2
COMMENTS
MATHEMATICA
a[0] = 0; a[n_] := a[n] = Block[{k = 1, idm = IntegerDigits[ a[n - 1], 3], t = a@# & /@ Range[n - 1]}, Label[ start]; While[ MemberQ[t, k], k++]; While[ Select[ Permutations[ Join[ idm, IntegerDigits[k, 3]]], #[[1]] != 0 && # == Reverse@# &] == {}, k++; Goto[ start]]; k]; s = Array[a, 100, 0]
CROSSREFS
KEYWORD
nonn,base,easy
AUTHOR
N. J. A. Sloane and Robert G. Wilson v, Nov 15 2013
STATUS
approved