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A335072
Numbers with property that if you remove any digit and subtract 1 the result is prime.
1
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
1,1
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..363 (all terms up to 10 million)
EXAMPLE
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.
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 *)
CROSSREFS
Cf. A034895.
Sequence in context: A112817 A115394 A344143 * A260678 A329658 A344139
KEYWORD
nonn,base
AUTHOR
John Ryder, May 30 2020
STATUS
approved