A065712 - OEIS

A065712

Number of 1's in decimal expansion of 2^n.

1, 0, 0, 0, 1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 0, 2, 1, 0, 1, 1, 1, 0, 2, 0, 1, 2, 0, 1, 2, 1, 0, 0, 3, 0, 1, 1, 0, 1, 3, 1, 3, 0, 3, 1, 1, 1, 2, 2, 2, 2, 0, 1, 3, 1, 0, 4, 4, 0, 3, 1, 3, 0, 3, 3, 0, 2, 2, 3, 6, 3, 1, 0, 2, 3, 3, 5, 1, 1, 5, 3, 1, 2, 5, 1, 4, 2, 2, 5, 2, 0, 5, 3, 1, 6, 2, 2, 4, 5, 2

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OFFSET

0,18

COMMENTS

2^17 = 131072 so a(17)=2.

LINKS

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

MATHEMATICA

Table[ Count[ IntegerDigits[2^n], 1], {n, 0, 100} ]

Table[DigitCount[2^n, 10, 1], {n, 0, 120}] (* Harvey P. Dale, Aug 15 2014 *)

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) }