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A124210
a(n) is the number of positive integers k such that sum of digits of 2^k equals n.
0
0, 1, 0, 1, 1, 0, 2, 2, 0, 1, 1, 0, 1, 2, 0, 0, 0, 0, 2, 1, 0, 1, 0, 0, 2, 2, 0, 0, 2, 0, 1, 0, 0, 0, 1, 0, 2, 0, 0, 1, 2, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 0, 0, 0, 0, 2, 0, 2, 1, 0, 2, 2, 0, 1, 1, 0, 1, 1, 0, 3, 1, 0, 1, 1, 0, 1, 2, 0, 1, 2, 0, 2, 0, 0, 2, 2, 0, 1, 2, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1
OFFSET
1,7
EXAMPLE
a(7) = 2 because 2^4 = 16 and 2^10 = 1024 and the sums of the digits of these two numbers are 7; and there are no other numbers like this.
MATHEMATICA
Table[Length[Select[Range[1000], Plus @@ IntegerDigits[2^# ] == n &]], {n, 100}]
CROSSREFS
Sequence in context: A219946 A117449 A004594 * A287447 A110568 A088689
KEYWORD
base,nonn
AUTHOR
Tanya Khovanova, Dec 13 2006
STATUS
approved