A096240
Number of n-digit base-7 deletable primes.
Original entry on oeis.org
3, 7, 21, 59, 184, 534, 1620, 4889, 15607, 50138, 165569, 551580, 1860565, 6345080
Offset: 1
-
b = 7; a = {3}; d = {2, 3, 5};
For[n = 2, n <= 7, n++,
p = Select[Range[b^(n - 1), b^n - 1], PrimeQ[#] &];
ct = 0;
For[i = 1, i <= Length[p], i++,
c = IntegerDigits[p[[i]], b];
For[j = 1, j <= n, j++,
t = Delete[c, j];
If[t[[1]] == 0, Continue[]];
If[MemberQ[d, FromDigits[t, b]], AppendTo[d, p[[i]]]; ct++;
Break[]]]];
AppendTo[a, ct]];
a (* Robert Price, Nov 12 2018 *)
A096241
Number of n-digit base-8 deletable primes.
Original entry on oeis.org
4, 14, 50, 238, 1123, 5792, 30598, 166056, 927639, 5308458, 30984757
Offset: 1
-
b = 8; a = {4}; d = {2, 3, 5, 7};
For[n = 2, n <= 5, n++,
p = Select[Range[b^(n - 1), b^n - 1], PrimeQ[#] &];
ct = 0;
For[i = 1, i <= Length[p], i++,
c = IntegerDigits[p[[i]], b];
For[j = 1, j <= n, j++,
t = Delete[c, j];
If[t[[1]] == 0, Continue[]];
If[MemberQ[d, FromDigits[t, b]], AppendTo[d, p[[i]]]; ct++;
Break[]]]];
AppendTo[a, ct]];
a (* Robert Price, Nov 13 2018 *)
-
from sympy import isprime
def ok(n, prevset, base=8):
if not isprime(n): return False
s = oct(n)[2:]
si = (s[:i]+s[i+1:] for i in range(len(s)))
return any(t[0] != '0' and int(t, base) in prevset for t in si)
def afind(terms):
s, snxt = {2, 3, 5, 7}, set()
print(len(s), end=", ")
for n in range(2, terms+1):
for i in range(8**(n-1), 8**n):
if ok(i, s):
snxt.add(i)
s, snxt = snxt, set()
print(len(s), end=", ")
afind(7) # Michael S. Branicky, Jan 14 2022
A096242
Number of n-digit base-9 deletable primes.
Original entry on oeis.org
4, 14, 58, 221, 911, 3638, 14687, 61435, 262189, 1140171
Offset: 1
-
b = 9; a = {4}; d = {2, 3, 5, 7};
For[n = 2, n <= 5, n++,
p = Select[Range[b^(n - 1), b^n - 1], PrimeQ[#] &];
ct = 0;
For[i = 1, i <= Length[p], i++,
c = IntegerDigits[p[[i]], b];
For[j = 1, j <= n, j++,
t = Delete[c, j];
If[t[[1]] == 0, Continue[]];
If[MemberQ[d, FromDigits[t, b]], AppendTo[d, p[[i]]]; ct++;
Break[]]]];
AppendTo[a, ct]];
a (* Robert Price, Nov 13 2018 *)
A096244
Number of n-digit base-11 deletable primes.
Original entry on oeis.org
4, 16, 73, 288, 1117, 4472, 18120, 74643, 315174, 1348936
Offset: 1
-
b = 11; a = {4}; d = {2, 3, 5, 7};
For[n = 2, n <= 5, n++,
p = Select[Range[b^(n - 1), b^n - 1], PrimeQ[#] &];
ct = 0;
For[i = 1, i <= Length[p], i++,
c = IntegerDigits[p[[i]], b];
For[j = 1, j <= n, j++,
t = Delete[c, j];
If[t[[1]] == 0, Continue[]];
If[MemberQ[d, FromDigits[t, b]], AppendTo[d, p[[i]]]; ct++;
Break[]]]];
AppendTo[a, ct]];
a (* Robert Price, Nov 13 2018 *)
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