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

Offset

1,1

Links

Table of n, a(n) for n=1..18.

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 *)

Crossrefs

Cf. A068690, A068691.

Sequence in context: A071363 A174616 A089394 * A178006 A053302 A068877

Adjacent sequences: A068689 A068690 A068691 * A068693 A068694 A068695

Keyword

base,nonn

Author

Amarnath Murthy, Mar 03 2002

Extensions

More terms from Sascha Kurz, Mar 26 2002

Status

approved