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A067469 Numbers k such that 2 is the first digit of 2^k. 4
1, 8, 11, 18, 21, 28, 31, 38, 41, 48, 51, 58, 61, 68, 71, 81, 91, 101, 104, 111, 114, 121, 124, 131, 134, 141, 144, 151, 154, 161, 164, 171, 174, 184, 194, 197, 204, 207, 214, 217, 224, 227, 234, 237, 244, 247, 254, 257, 264, 267, 277, 287, 297, 300, 307, 310 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Muniru A Asiru, Table of n, a(n) for n = 1..5000

MATHEMATICA

Select[Range@ 310, First@ IntegerDigits[2^#] == 2 &] (* Michael De Vlieger, Oct 15 2018 *)

PROG

(PARI) is(n)=digits(2^n)[1]==2 \\ Charles R Greathouse IV, Jul 29 2013

(GAP) Filtered([1..310], n->ListOfDigits(2^n)[1]=2); # Muniru A Asiru, Oct 14 2018

CROSSREFS

Cf. A067480.

Sequence in context: A299979 A291663 A306277 * A237767 A284324 A205856

Adjacent sequences:  A067466 A067467 A067468 * A067470 A067471 A067472

KEYWORD

nonn,base

AUTHOR

Benoit Cloitre, Feb 22 2002

STATUS

approved

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Last modified January 27 14:39 EST 2020. Contains 331295 sequences. (Running on oeis4.)