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A245404
Number of nonnegative integers with property that their base 7/2 expansion (see A024639) has n digits.
0
7, 21, 70, 245, 861, 3010, 10535, 36876, 129066, 451731, 1581055, 5533696, 19367936, 67787776, 237257216, 830400256, 2906400896, 10172403136, 35603410976, 124611938416, 436141784456, 1526496245596, 5342736859586, 18699579008551, 65448526529925, 229069842854741
OFFSET
0,1
EXAMPLE
The numbers 7-27 are represented by 20, 21, 22, 23, 24, 25, 26, 40, 41, 42, 43, 44, 45, 46, 60, 61, 62, 63, 64, 65, 66 respectively in base 7/2. These are the only integers with two digits, and so a(2)=21.
PROG
(Sage)
A=[1]
for i in [1..60]:
A.append(ceil((7-2)/2*sum(A)))
[7*x for x in A]
CROSSREFS
Sequence in context: A152766 A152671 A113859 * A215494 A146533 A208534
KEYWORD
nonn,base
AUTHOR
James Van Alstine, Jul 21 2014
STATUS
approved