A335072 Numbers with property that if you remove any digit and subtract 1 the result is prime.
33, 34, 36, 38, 43, 44, 46, 48, 63, 64, 66, 68, 83, 84, 86, 88, 124, 142, 144, 148, 184, 204, 244, 308, 320, 380, 424, 442, 444, 448, 484, 544, 608, 620, 680, 724, 742, 744, 804, 844, 908, 980, 1104, 1140, 2284, 2728, 2824, 3608, 3908, 4440, 4444, 4588, 4644
Offset: 1
Examples
33 is a term: remove any digit to be left with 3. Subtract 1 gives 2, which is prime. 4444 is a term: remove any digit to be left with 444. Subtract 1 to be left with 443, which is prime. 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.
Links
- Harvey P. Dale, Table of n, a(n) for n = 1..363 (all terms up to 10 million)
Crossrefs
Cf. A034895.
Programs
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Maple
q:= n-> (s-> andmap(i-> isprime(parse(cat(0,s[1..i-1], s[i+1..-1]))-1), [$1..length(s)]))(""||n): select(q, [$1..5000])[]; # Alois P. Heinz, May 30 2020 -
Mathematica
rdpQ[x_]:=AllTrue[FromDigits/@Table[Drop[IntegerDigits[x],{n}],{n,IntegerLength[ x]}]-1,PrimeQ]; Select[Range[4700],rdpQ] (* Harvey P. Dale, Aug 21 2020 *)