OFFSET
1,2
COMMENTS
No term ends with zero.
EXAMPLE
a(1) = 1, k = 1, and the product 1 is odd;
a(2) = 11, k = 1, and the product 1 is odd;
a(3) = 3, k = 3, and the product 1*1*3 (= 3) is odd;
a(4) = 5, k = 5, and the product 1*1*1*3*5 (= 15) is odd;
a(5) = 13, k = 3, and the product 5*1*3 (= 15) is odd;
a(6) = 7, k = 7, and the product 1*1*3*5*1*3*7 (= 315) is odd; etc.
MATHEMATICA
a[1]=1; a[n_]:=a[n]=Block[{t=1}, While[(k=t~Mod~10; k>Length[s=Flatten[IntegerDigits/@Join[Array[a, n-1], {t}]]])||k<1||MemberQ[Array[a, n-1], t]||EvenQ[Times@@(s[[-k;; ]])], t++]; t]; Array[a, 70] (* Giorgos Kalogeropoulos, May 10 2022 *)
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Eric Angelini and Carole Dubois, May 30 2021
STATUS
approved