|
%I #24 Feb 03 2022 21:34:03
%S 2,4,8,16,18,32,38,46,48,62,66,80,90,102,120,138,158,160,180,212,242,
%T 278,324,364,436,482,574,576,658,736,738,882,892,900,972,974,976,1162,
%U 1164,1318,1320,1524,1526,1528,1762,1788,1796,1982,2342,2344,2346,2386,2392,2634,3110
%N Numbers k such that Sum_{j=1..k} A006513(j) = 3*k/2.
%H Michel Marcus, <a href="/A076057/b076057.txt">Table of n, a(n) for n = 1..858</a>
%F a(n) seems to be asymptotic to c*n^2 with 1/2 < c < 1.
%o (PARI) f(n) = if (n%2, (3*n+1)/2, n/2); \\ A014682
%o g(n) = my(last = n); while (1, my(new = f(f(last))); if (new == last, return(new)); last = new;); \\ A006513
%o isok(m) = !(m%2) && (sum(k=1, m, g(k)) == 3*m/2); \\ _Michel Marcus_, Feb 03 2022
%o (PARI) f(n) = if (n%2, (3*n+1)/2, n/2); \\ A014682
%o g(n) = my(last = n); while (1, my(new = f(f(last))); if (new == last, return(new)); last = new;); \\ A006513
%o lista(nn) = {my(v = vector(nn, k, g(k)), w = vector(nn)); w[1] = v[1]; for (i=2, nn, w[i] = w[i-1] + v[i];); forstep (i=2, nn, 2, if (w[i] == 3*i/2, print1(i, ", ")););} \\ _Michel Marcus_, Feb 03 2022
%Y Cf. A006513, A014682.
%K nonn
%O 1,1
%A _Benoit Cloitre_, Oct 30 2002
%E More terms from _Michel Marcus_, Feb 03 2022
|
