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%I #12 May 05 2020 17:08:32
%S 0,0,1,4,7,14,17,28,35,46,53,72,79,102,113,128,143,174,185,220,235,
%T 258,277,320,335,374,397,432,455,510,525,584,615,654,685,732,755,826,
%U 861,908,939,1018,1041,1124,1163,1210,1253,1344,1375,1458,1497
%N a(n) = A196227(n)/2.
%C See A210000 for a guide to related sequences.
%p a:= proc(n) option remember; `if`(n<2, 0,
%p a(n-1)-1 + 2*numtheory[phi](n))
%p end:
%p seq(a(n), n=0..60); # _Alois P. Heinz_, May 05 2020
%t a = 1; b = n; z1 = 50;
%t t[n_] := t[n] = Flatten[Table[w*z - x*y, {w, a, b}, {x, a, b}, {y, a, b}, {z, a, b}]]
%t c[n_, k_] := c[n, k] = Count[t[n], k]
%t Table[c[n, 0], {n, 0, z1}] (* A134506 *)
%t Table[c[n, 1], {n, 0, z1}] (* A196227 *)
%t %/2 (* A209978 *)
%t Table[2 c[n, 1], {n, 0, z1}](* A209979 *)
%t Table[c[n, 2], {n, 0, z1}] (* A197168 *)
%t %/2 (* A209980 *)
%t Table[c[n, 3], {n, 0, z1}] (* A210001 *)
%t Table[c[n, 4], {n, 0, z1}] (* A210002 *)
%t Table[c[n, 5], {n, 0, z1}] (* A210027 *)
%Y Cf. A196227, A210000.
%K nonn
%O 0,4
%A _Clark Kimberling_, Mar 16 2012
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