A049793 a(n) = T(n,n-1), array T as in A049790.

1, 2, 4, 9, 13, 22, 27, 39, 47, 61, 71, 91, 100, 122, 137, 160, 175, 205, 220, 253, 272, 304, 326, 368, 386, 427, 455, 497, 523, 575, 598, 651, 683, 733, 768, 830, 856, 918, 959, 1021, 1056, 1129, 1162, 1236, 1281, 1347, 1393

Offset: 2

Author

Clark Kimberling

Keywords

• nonn

Links

• G. C. Greubel, Table of n, a(n) for n = 2..1000

Crossrefs

Cf. A049790, A049791, A049792, A049794, A049795, A049796.

Programs

GAP

a:= function(n)
    if n=2 then return 1;
    else return Sum([1..n-2], j-> Int((n-1)/Int((n-2)/j)) );
    fi; end;
List([2..60], n-> a(n) ); # G. C. Greubel, Dec 10 2019

Magma

[n eq 2 select 1 else (&+[Floor((n-1)/Floor((n-2)/j)): j in [1..n-2]]): n in [2..60]]; // G. C. Greubel, Dec 10 2019

Maple

seq( `if`(n=2, 1, add(floor((n-1)/floor((n-2)/j)), j=1..n-2)), n=2..60); # G. C. Greubel, Dec 10 2019

Mathematica

Table[If[n==2, 1, Sum[Floor[(n-1)/Floor[(n-2)/j]], {j,n-2}]], {n, 2,60}] (* G. C. Greubel, Dec 10 2019 *)

PARI

a(n) = if(n==2, 1, sum(j=1,n-2, (n-1)\((n-2)\j)) );
vector(60, n, a(n+1) ) \\ G. C. Greubel, Dec 10 2019

Sage

def a(n):
    if (n==2): return 1
    else: return sum(floor((n-1)/floor((n-2)/j)) for j in (1..n-2))
[a(n) for n in (2..60)] # G. C. Greubel, Dec 10 2019