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A195464
a(n) = 2^(4*n + 3) + 2*4^n + 3.
1
13, 139, 2083, 32899, 524803, 8390659, 134225923, 2147516419, 34359869443, 549756338179, 8796095119363, 140737496743939, 2251799847239683, 36028797153181699, 576460752840294403, 9223372039002259459, 147573952598266347523, 2361183241469182345219
OFFSET
0,1
COMMENTS
Binary numbers of form 1j1i11 where j and i are the number of 0's, n is the index, i = 2*n+1, j = 2*n+3.
FORMULA
a(n) = 2^(4*n+3) + A188161(n).
From Alexander R. Povolotsky, Sep 19 2011: (Start)
a(n+2) = 20*a(n+1) - 64*a(n) + 135.
G.f.: (-13 + 134*x - 256*x^2)/(-1 + 21*x - 84*x^2 + 64*x^3). (End)
a(n) = 3 + A026244(n+1). - Bruno Berselli, Sep 19 2011
EXAMPLE
Terms starting from n=1 written in binary are 10001011, 100000100011, 1000000010000011, 10000000001000000011.
PROG
(Magma) [2^(4*n + 3) + 2*4^n + 3: n in [0..20]]; // Vincenzo Librandi, Sep 30 2011
CROSSREFS
Cf. A188161.
Sequence in context: A351812 A300694 A193708 * A365999 A064103 A266630
KEYWORD
nonn,easy
AUTHOR
Brad Clardy, Sep 19 2011
STATUS
approved