OFFSET
1,2
COMMENTS
The nonprime digits are 0, 1, 4, 6, 8 and 9. This is the lexicographically earliest sequence of distinct nonnegative terms with this property and also a permutation of the nonnegative integers.
LINKS
EXAMPLE
a(1) + a(2) = 0 + 2 = 2 (no nonprime digit is present);
a(2) + a(3) = 2 + 1 = 3 (no nonprime digit is present);
a(3) + a(4) = 1 + 4 = 5 (no nonprime digit is present);
a(4) + a(5) = 4 + 3 = 7 (no nonprime digit is present);
a(5) + a(6) = 3 + 19 = 22 (no nonprime digit is present); etc.
MAPLE
N:= 1000: # for terms before the first term > N
S:= [$1...N]:
V:=Vector(N):
for n from 2 to N do
for i from 1 to N+2-n do
s:= S[i];
if convert(convert(V[n-1]+s, base, 10), set) subset {2, 3, 5, 7} then
V[n]:= s;
S:= subsop(i=NULL, S);
break
fi;
od;
if V[n] = 0 then break fi
od:
convert(V[1..n-1], list); # Robert Israel, Nov 18 2020
MATHEMATICA
Block[{a = {0}}, Do[Block[{k = 1}, While[Nand[FreeQ[a, k], NoneTrue[IntegerDigits@ Total[a[[-1]] + k], ! PrimeQ@ # &]], k++]; AppendTo[a, k]], {i, 2, 75}]; a] (* Michael De Vlieger, Nov 12 2020 *)
CROSSREFS
KEYWORD
AUTHOR
Eric Angelini and Carole Dubois, Nov 11 2020
STATUS
approved