A335072 - OEIS

%I #31 Jul 23 2023 01:53:47

%S 33,34,36,38,43,44,46,48,63,64,66,68,83,84,86,88,124,142,144,148,184,

%T 204,244,308,320,380,424,442,444,448,484,544,608,620,680,724,742,744,

%U 804,844,908,980,1104,1140,2284,2728,2824,3608,3908,4440,4444,4588,4644

%N Numbers with property that if you remove any digit and subtract 1 the result is prime.

%H Harvey P. Dale, <a href="/A335072/b335072.txt">Table of n, a(n) for n = 1..363</a> (all terms up to 10 million)

%e 33 is a term: remove any digit to be left with 3. Subtract 1 gives 2, which is prime.

%e 4444 is a term: remove any digit to be left with 444. Subtract 1 to be left with 443, which is prime.

%e 28 is not a term: remove any digit to be left with 2 or 8. Subtract 1 to be left with 1 or 7. 1 is not prime.

%p q:= n-> (s-> andmap(i-> isprime(parse(cat(0,s[1..i-1],

%p             s[i+1..-1]))-1), [$1..length(s)]))(""||n):

%p select(q, [$1..5000])[];  # _Alois P. Heinz_, May 30 2020

%t rdpQ[x_]:=AllTrue[FromDigits/@Table[Drop[IntegerDigits[x],{n}],{n,IntegerLength[ x]}]-1,PrimeQ]; Select[Range[4700],rdpQ] (* _Harvey P. Dale_, Aug 21 2020 *)

%Y Cf. A034895.

%K nonn,base

%O 1,1

%A _John Ryder_, May 30 2020