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A197432 a(n) = Sum_{k>=0} A030308(n,k)*C(k) where C(k) is the k-th Catalan number (A000108). 1

%I #16 Jul 23 2017 21:55:44

%S 0,1,1,2,2,3,3,4,5,6,6,7,7,8,8,9,14,15,15,16,16,17,17,18,19,20,20,21,

%T 21,22,22,23,42,43,43,44,44,45,45,46,47,48,48,49,49,50,50,51,56,57,57,

%U 58,58,59,59,60,61,62,62,63,63,64,64,65

%N a(n) = Sum_{k>=0} A030308(n,k)*C(k) where C(k) is the k-th Catalan number (A000108).

%C Replace 2^k with A000108(k) in binary expansion of n.

%F G.f.: (1/(1 - x))*Sum_{k>=0} Catalan number(k)*x^(2^k)/(1 + x^(2^k)). - _Ilya Gutkovskiy_, Jul 23 2017

%e 11 = 1011_2, so a(11) = 1*1 + 1*1 + 0*2 + 1*5 = 7.

%Y Cf. A000108, A030308, A197433.

%Y Other sequences that are built by replacing 2^k in binary representation with other numbers: A022290 (Fibonacci), A029931 (natural numbers), A059590 (factorials), A089625 (primes), A197354 (odd numbers).

%K nonn,easy

%O 0,4

%A _Philippe Deléham_, Oct 15 2011

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Last modified March 19 06:05 EDT 2024. Contains 370952 sequences. (Running on oeis4.)