OFFSET
1,1
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
EXAMPLE
26 is a member as the three numbers 126, 216 and 261 obtained by placing a 1 at all possible places are composite.
MAPLE
anz := 0:for i from 2 to 1500 do b := convert(i, base, 10):s := sum(b[l], l=1..nops(b)): ok := true:for j from 0 to nops(b) do q := sum(b[k]*10^(k-1), k=1..j):q := q+10^(j): q := q+sum(b[k]*10^k, k=j+1..nops(b)): if(isprime(q)) then ok := false:fi:od: if(ok=true) then anz := anz+1:a[anz] := i:fi:od:seq(a[l], l=1..anz);
MATHEMATICA
Select[Range[200], AllTrue[FromDigits/@Table[Insert[IntegerDigits[#], 1, n], {n, IntegerLength[ #]+ 1}], CompositeQ]&] (* Harvey P. Dale, Nov 14 2023 *)
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Amarnath Murthy, May 11 2002
EXTENSIONS
Corrected and extended by Sascha Kurz, Jan 26 2003
STATUS
approved