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A065718 Number of 7's in decimal expansion of 2^n. 11
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 1, 1, 0, 0, 3, 0, 1, 2, 0, 1, 2, 1, 1, 0, 2, 1, 3, 2, 3, 1, 3, 0, 0, 1, 1, 1, 4, 2, 3, 0, 0, 1, 2, 2, 0, 2, 4, 2, 3, 2, 1, 0, 2, 3, 3, 1, 3, 3, 2, 2, 2, 0, 1, 3, 2, 5, 3, 3, 2, 2, 3, 1, 3, 3, 1, 2, 4, 2, 2, 2, 2, 5, 2, 1, 2, 5, 2, 4, 4, 2, 3 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,25

COMMENTS

2^15 = 32768 so a(15)=1.

LINKS

Harry J. Smith, Table of n, a(n) for n = 0..1000

MATHEMATICA

Table[ Count[ IntegerDigits[2^n], 7], {n, 0, 100} ]

PROG

(PARI) Count(x, d)= { local(c=0, f); while (x>9, f=x-10*(x\10); if (f==d, c++); x\=10); if (x==d, c++); return(c) } { for (n=0, 1000, a=Count(2^n, 7); write("b065718.txt", n, " ", a) ) } \\ Harry J. Smith, Oct 27 2009

(PARI) a(n) = #select(x->(x==7), digits(2^n)); \\ Michel Marcus, Jun 15 2018

CROSSREFS

Cf. 0's A027870, 1's A065712, 2's A065710, 3's A065714, 4's A065715, 5's A065716, 6's A065717, 8's A065719, 9's A065744.

Sequence in context: A303301 A160499 A274876 * A025428 A199176 A021336

Adjacent sequences:  A065715 A065716 A065717 * A065719 A065720 A065721

KEYWORD

nonn,base

AUTHOR

Benoit Cloitre, Dec 04 2001

EXTENSIONS

More terms from Robert G. Wilson v, Dec 07 2001

STATUS

approved

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Last modified May 19 17:48 EDT 2019. Contains 323395 sequences. (Running on oeis4.)