A244848 Least number k > 0 such that 2^k begins with exactly n consecutive decreasing digits.

1, 5, 201, 664, 37025, 78171, 3944467, 138044449, 1910108568, 1641098748

Offset

1,2

Links

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

Example

2^201 begins "32138760885...". Since it starts with a run of 3 consecutive decreasing digits and 201 is the smallest power to have this property, a(3) = 201.

Prog

(Python)
def a(n):
..for k in range(1, 10**5):
....st = str(2**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. A244849, A244851, A244852.

Sequence in context: A106990 A128791 A303136 * A041775 A093976 A337579

Adjacent sequences: A244845 A244846 A244847 * A244849 A244850 A244851

Keyword

nonn,base,fini,full

Author

Derek Orr, Jul 07 2014

Extensions

a(7)-a(10) from Hiroaki Yamanouchi, Jul 10 2014

Status

approved