A244851 Least number k > 0 such that 3^k begins with exactly n consecutive decreasing digits.

1, 7, 314, 1655, 11569, 383374, 3052836, 31843469, 458415111, 164840426684

Offset

1,2

Comments

The leading digit of the resulting powers of 3 are: 3, 2, 6, 4, 6, 7, 8, 7, 8, 9. - Michel Marcus, Jul 11 2014

Links

Table of n, a(n) for n=1..10.

Example

3^7 = 2187 begins with 2 consecutive decreasing digits ('21'). Thus a(2) = 7.

Prog

(Python)
def a(n):
..for k in range(1, 10**5):
....st = str(3**k)
....count = 0
....if len(st) > n:
......for i in range(len(st)):
........if int(st[i]) == int(st[i+1])+1:
..........count += 1
........else:
..........break
......if count == n:
........return k
n = 0
while n < 10:
..print(a(n), end=', ')
..n += 1

Crossrefs

Cf. A244848, A244849, A244852.

Sequence in context: A364479 A171148 A219267 * A082160 A220278 A163437

Adjacent sequences: A244848 A244849 A244850 * A244852 A244853 A244854

Keyword

nonn,base,fini,full

Author

Derek Orr, Jul 07 2014

Extensions

a(6)-a(10) from Hiroaki Yamanouchi, Jul 11 2014

Status

approved