A046272
Largest prime substring in 6^n (0 if none).
Original entry on oeis.org
0, 0, 3, 2, 29, 7, 5, 7993, 67961, 769, 604661, 2797, 78233, 1306069, 783641, 7018498457, 2821109, 692665944473, 66841, 609359, 4400629, 21936950640377, 16217038422671, 3022305360281, 73838133832161689, 992970137, 170581728179
Offset: 0
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Join[{0,0},Table[SelectFirst[Reverse[Union[FromDigits/@Flatten[Table[ Partition[ IntegerDigits[ 6^k],n,1],{n,IntegerLength[6^k]-1}],1]]],PrimeQ],{k,2,28}]] (* Harvey P. Dale, Mar 08 2023 *)
A050727
Numbers k such that the decimal expansion of 6^k contains no pair of consecutive equal digits (probably finite).
Original entry on oeis.org
0, 1, 2, 3, 4, 8, 11, 13, 14, 15, 26
Offset: 1
6^26 = 170581728179578208256 where no consecutive digits are equal.
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Select[Range[120],!MemberQ[Differences[IntegerDigits[6^#]],0]&] (* Harvey P. Dale, Oct 17 2011 *)
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isok(n) = {my(d = digits(6^n), c = d[1]); for (i=2, #d, if (d[i] == c, return (0)); c = d[i];); return (1);} \\ Michel Marcus, Oct 16 2019
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try: from gmpy2 import mpz; x = mpz(1)
except: x = 1
print(0)
k = 1
while True:
print('\b'*42 + str(k), end='')
x *= 6 # x == 6**k
y, flag = x, True
y, a = divmod(y, 10)
while y > 6:
b = a
y, a = divmod(y, 10)
if a == b:
flag = False
break
if flag: print()
k += 1
# Lucas A. Brown, Mar 02 2024
Showing 1-2 of 2 results.
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