A321910 - OEIS

A321910

Base-7 deletable primes (written in base 10).

2, 3, 5, 17, 19, 23, 31, 37, 41, 47, 101, 103, 131, 137, 139, 149, 163, 167, 191, 199, 223, 227, 233, 241, 251, 263, 293, 311, 313, 317, 331, 691, 709, 719, 727, 733, 787, 823, 853, 877, 887, 919, 929, 937, 977, 983, 997, 1013, 1019, 1021, 1031, 1049, 1129, 1171, 1367, 1399, 1409, 1511

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OFFSET

1,1

COMMENTS

A prime p is a base-b deletable prime if when written in base b it has the property that removing some digit leaves either the empty string or another deletable prime.

Deleting a digit cannot leave any leading zeros in the new string. For example, deleting the 2 in 2003 to obtain 003 is not allowed.

LINKS

Robert Price, Table of n, a(n) for n = 1..808

MATHEMATICA

b = 7; d = {};

p = Select[Range[2, 10000], PrimeQ[#] &];

For[i = 1, i <= Length[p], i++,

c = IntegerDigits[p[[i]], b];

If[Length[c] == 1, AppendTo[d, p[[i]]]; Continue[]];

For[j = 1, j <= Length[c], j++,

t = Delete[c, j];

If[t[[1]] == 0, Continue[]];