A151791 - OEIS

%I #18 Nov 01 2022 09:04:58

%S 1,7,7,42,7,42,42,252,7,42,42,252,42,252,252,1512,7,42,42,252,42,252,

%T 252,1512,42,252,252,1512,252,1512,1512,9072,7,42,42,252,42,252,252,

%U 1512,42,252,252,1512,252,1512,1512,9072,42,252,252,1512,252,1512,1512,9072,252

%N a(1)=1; for n > 1, a(n) = 7*6^(wt(n-1)-1).

%C wt(n) is the Hamming weight = binary weight of n (A000120).

%H Michael De Vlieger, <a href="/A151791/b151791.txt">Table of n, a(n) for n = 1..8192</a>

%e From _Omar E. Pol_, Feb 26 2015: (Start)

%e Written as an irregular triangle in which the row lengths are the terms of A011782 the sequence begins:

%e 1;

%e 7;

%e 7,42;

%e 7,42,42,252;

%e 7,42,42,252,42,252,252,1512;

%e 7,42,42,252,42,252,252,1512,42,252,252,1512,252,1512,1512,9072;

%e 7,42,42,252,42,252,252,1512,42,252,252,1512,252,1512,1512,9072,42,252,252,1512,252,1512,1512,9072,252,...

%e It appears that the right border gives A003949.

%e It appears that the row sums give A000420.

%e (End)

%t a[n_] := 7*6^(Total@ IntegerDigits[n - 1, 2] - 1); a[1] = 1; Array[a, 57] (* _Michael De Vlieger_, Nov 01 2022 *)

%Y Cf. A011782, A000120, A000420, A151792 (partial sums).

%K nonn,tabf

%O 1,2

%A _N. J. A. Sloane_, Jun 25 2009