A077713
a(1) = 3; thereafter a(n) = the smallest prime of the form d0...0a(n-1), where d is a single digit, or 0 if no such prime exists.
Original entry on oeis.org
3, 13, 113, 2113, 12113, 612113, 50612113, 1050612113, 6001050612113, 26001050612113, 1026001050612113, 6000001026001050612113, 500006000001026001050612113, 600500006000001026001050612113, 1600500006000001026001050612113, 6001600500006000001026001050612113
Offset: 1
a(7) = 50612113: deleting 5 gives 612113 = a(6).
-
a:= proc(n) option remember; local k, m, d, p;
if n=1 then 3 else k:= a(n-1);
for m from length(k) do
for d to 9 do p:= k +d*10^m;
if isprime(p) then return p fi
od od
fi
end:
seq(a(n), n=1..20); # Alois P. Heinz, Jan 12 2015
-
from sympy import isprime
from itertools import islice
def agen(an=3):
while True:
yield an
pow10 = 10**len(str(an))
while True:
found = False
for t in range(pow10+an, 10*pow10+an, pow10):
if isprime(t):
an = t; found = True; break
if found: break
pow10 *= 10
print(list(islice(agen(), 16))) # Michael S. Branicky, Jun 23 2022
A077714
a(1) = 1; thereafter a(n) = the smallest prime of the form d0...0a(n-1), where d is a single digit, or 0 if no such prime exists.
Original entry on oeis.org
1, 11, 211, 4211, 34211, 234211, 4234211, 304234211, 9304234211, 209304234211, 7209304234211, 37209304234211, 3037209304234211, 23037209304234211, 323037209304234211, 70000323037209304234211, 300070000323037209304234211, 600300070000323037209304234211
Offset: 1
a(8) = 304234211; deleting 3 gives 4234211 = a(7).
-
a:= proc(n) option remember; local k, m, d, p;
if n=1 then 1 else k:= a(n-1);
for m from length(k) do
for d to 9 do p:= k +d*10^m;
if isprime(p) then return p fi
od od
fi
end:
seq(a(n), n=1..20); # Alois P. Heinz, Jan 12 2015
-
from sympy import isprime
from itertools import islice
def agen(an=1):
while True:
yield an
pow10 = 10**len(str(an))
while True:
found = False
for t in range(pow10+an, 10*pow10+an, pow10):
if isprime(t):
an = t; found = True; break
if found: break
pow10 *= 10
print(list(islice(agen(), 18))) # Michael S. Branicky, Jun 23 2022
A077715
a(1) = 7; thereafter a(n) = the smallest prime of the form d0...0a(n-1), where d is a single digit, or 0 if no such prime exists.
Original entry on oeis.org
7, 17, 317, 6317, 26317, 126317, 2126317, 72126317, 372126317, 5372126317, 305372126317, 9305372126317, 409305372126317, 20409305372126317, 100020409305372126317, 9100020409305372126317, 209100020409305372126317, 40209100020409305372126317
Offset: 1
-
a:= proc(n) option remember; local k, m, d, p;
if n=1 then 7 else k:= a(n-1);
for m from length(k) do
for d to 9 do p:= k +d*10^m;
if isprime(p) then return p fi
od od
fi
end:
seq(a(n), n=1..20); # Alois P. Heinz, Jan 12 2015
-
from sympy import isprime
from itertools import islice
def agen(an=7):
while True:
yield an
pow10 = 10**len(str(an))
while True:
found = False
for t in range(pow10+an, 10*pow10+an, pow10):
if isprime(t):
an = t; found = True; break
if found: break
pow10 *= 10
print(list(islice(agen(), 18))) # Michael S. Branicky, Jun 23 2022
Showing 1-3 of 3 results.
Comments