A104388
Lesser of two successive primes the average of which is a repdigit.
Original entry on oeis.org
3, 5, 7, 97, 109, 4441, 111111109, 555555555551, 9999999999999937, 111111111111111091, 444444444444444419, 555555555555555555491, 777777777777777777777767, 333333333333333333333333333333293, 444444444444444444444444444444444391
Offset: 1
-
from itertools import count, islice
from sympy import isprime, prevprime
def agen():
for d in count(1):
ru = int("1"*d)
for r in range(ru, 10*ru, ru):
if r > 2:
p = prevprime(r)
if isprime(r + (r-p)) and prevprime(r+(r-p)) == p:
yield p
print(list(islice(agen(), 15))) # Michael S. Branicky, Jun 30 2022
A104387
Larger of two successive primes the average of which is a repdigit.
Original entry on oeis.org
5, 7, 11, 101, 113, 4447, 111111113, 555555555559, 10000000000000061, 111111111111111131, 444444444444444469, 555555555555555555619, 777777777777777777777787, 333333333333333333333333333333373, 444444444444444444444444444444444497
Offset: 1
-
Union[Flatten[Table[NextPrime/@Select[FromDigits/@Table[PadLeft[{i},n,i], {n,45}], Mean[{NextPrime[#],NextPrime[#,-1]}]==#&], {i,9}]]] (* Harvey P. Dale, Jun 28 2011 *)
-
from itertools import count, islice
from sympy import isprime, prevprime
def agen():
for d in count(1):
ru = int("1"*d)
for r in range(ru, 10*ru, ru):
if r > 2:
p = prevprime(r)
if isprime(r + (r-p)) and prevprime(r+(r-p)) == p:
yield 2*r - p
print(list(islice(agen(), 15))) # Michael S. Branicky, Jun 30 2022
A104389
Repdigits which are the average of two successive primes.
Original entry on oeis.org
4, 6, 9, 99, 111, 4444, 111111111, 555555555555, 9999999999999999, 111111111111111111, 444444444444444444, 555555555555555555555, 777777777777777777777777, 333333333333333333333333333333333, 444444444444444444444444444444444444
Offset: 1
-
from itertools import count, islice
from sympy import isprime, prevprime
def agen():
for d in count(1):
ru = int("1"*d)
for r in range(ru, 10*ru, ru):
if r > 2:
p = prevprime(r)
if isprime(r + (r-p)) and prevprime(r+(r-p)) == p:
yield r
print(list(islice(agen(), 15))) # Michael S. Branicky, Jun 30 2022
Showing 1-3 of 3 results.
Comments