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A067497 Smallest power of 2 with n+1 digits (n>=0). Also n such that 1 is the first digit of 2^n. 5
0, 4, 7, 10, 14, 17, 20, 24, 27, 30, 34, 37, 40, 44, 47, 50, 54, 57, 60, 64, 67, 70, 74, 77, 80, 84, 87, 90, 94, 97, 100, 103, 107, 110, 113, 117, 120, 123, 127, 130, 133, 137, 140, 143, 147, 150, 153, 157, 160, 163, 167, 170, 173, 177, 180, 183, 187, 190, 193, 196 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..59.

FORMULA

a(n) = ceiling(n*log_2(10)). - Vladeta Jovovic, Jun 20 2002

MATHEMATICA

a[n_] := Block[{k = 0}, While[ Floor[Log[10, 2^k] + 1] < n, k++ ]; k]; Table[ a[n], {n, 1, 61}]

Table[Ceiling[n*Log[2, 10]], {n, 0, 59}] (* Jean-Fran├žois Alcover, Jan 29 2014, after Vladeta Jovovic *)

PROG

(PARI) for(n=0, 500, if(floor(2^n/10^(floor(n*log(2)/log(10))))==1, print1(n, ", ")))

(PARI) s=0, for(n=0, 200, l=length(Str(2^n)), if(l>s, print1(n, ", "), s=l))

(PARI) a(n) = ceil(n*log(10)/log(2)); \\ Michel Marcus, May 13 2017

CROSSREFS

Cf. A067480, A000079, A066343, A129344.

Sequence in context: A080600 A198266 * A123384 A138813 A184625 A184118

Adjacent sequences:  A067494 A067495 A067496 * A067498 A067499 A067500

KEYWORD

base,nonn,easy

AUTHOR

Benoit Cloitre, Feb 22 2002

EXTENSIONS

Additional comments from Lekraj Beedassy, Jun 20 2002 and from Rick Shephard, Jun 27 2002

STATUS

approved

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Last modified May 30 06:51 EDT 2017. Contains 287302 sequences.