

A131552


Least positive power of 3 having exactly n consecutive 1's in its decimal representation.


2



4, 19, 93, 334, 841, 3404, 7271, 7720, 44152, 406774, 993948, 2421339, 8786439, 11387707
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OFFSET

1,1


COMMENTS

No more terms < 2*10^7.


LINKS

Table of n, a(n) for n=1..14.


EXAMPLE

a(3)=93 because 3^93 (i.e., 235655016338368235499067731945871638181119123) is the smallest power of 3 to contain a run of 3 consecutive ones in its decimal form.


MATHEMATICA

a = ""; Do[ a = StringJoin[a, "1"]; b = StringJoin[a, "1"]; k = 1; While[ StringPosition[ ToString[3^k], a] == {}  StringPosition[ ToString[3^k], b] != {}, k++ ]; Print[k], {n, 1, 10} ]


PROG

(Python)
def A131552(n):
....m, s = 1, '1'*n
....for i in range(1, 10**9):
........m *= 3
........if s in str(m):
............return i
....return "search limit reached." # Chai Wah Wu, Dec 11 2014


CROSSREFS

Sequence in context: A181950 A288687 A275751 * A122369 A005978 A083065
Adjacent sequences: A131549 A131550 A131551 * A131553 A131554 A131555


KEYWORD

more,nonn,base


AUTHOR

Shyam Sunder Gupta, Aug 26 2007


EXTENSIONS

a(11)a(14) from Lars Blomberg, Feb 02 2013
Definition edited by Chai Wah Wu, Dec 11 2014


STATUS

approved



