A068692 Largest n-digit prime with all even digits except for the least significant digit.

7, 89, 887, 8887, 88883, 888887, 8888861, 88888883, 888888887, 8888888809, 88888888801, 888888888887, 8888888888849, 88888888888889, 888888888888883, 8888888888888647, 88888888888888889, 888888888888888809, 8888888888888888881, 88888888888888888867, 888888888888888888683

Offset: 1

Author

Amarnath Murthy, Mar 03 2002

Keywords

• base
• nonn

Links

• Robert Israel, Table of n, a(n) for n = 1..996

Crossrefs

Cf. A068690, A068691.

Programs

Maple

for n from 1 to 40 do a := prevprime((10^n-1)/9*8+2):b := convert(a,base,10):c := true:for i from 2 to nops(b) do if((b[i] mod 2)>0) then c := false:end if:end do:while(c=false) do a := prevprime(a):b := convert(a,base,10):c := true:for i from 2 to nops(b) do if((b[i] mod 2)>0) then c := false:end if:end do:end do:q[n] := a:end do:seq(q[k],k=1..40);

Mathematica

nped[n_]:=Module[{p=NextPrime[9*10^n,-1]},While[AnyTrue[Most[ IntegerDigits[ p]],OddQ],p=NextPrime[p,-1]];p]; Array[nped,20,0] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jun 14 2018 *)

Extensions

More terms from Sascha Kurz, Mar 26 2002

More terms from Robert Israel, Jul 02 2025