A122205 Number of finite sequences b with b(0) = 1, b(i+1) = b(i)+d where d|b(i), ending with n.
1, 1, 1, 2, 2, 5, 5, 12, 17, 31, 31, 96, 96, 197, 324, 629, 629, 1695, 1695, 4374, 6266, 10671, 10671, 34402, 38776, 73274, 109371, 223510, 223510, 634267, 634267, 1527075, 2172013, 3699717, 4557494, 12736034, 12736034, 25473763, 38283071
Offset: 1
Keywords
Formula
a(1) = 1, for n>1, a(n) = sum_{d|n, d
A293665 a(0) = 1; a(n) = -Sum_{d|n} a(n-d).
1, -1, 0, -1, 0, -1, 1, -2, 0, -2, 2, -3, 1, -2, 2, -6, 2, -3, 7, -8, 2, -12, 12, -13, 0, -3, 4, -12, 17, -18, 19, -20, -19, -13, 34, -71, 54, -55, 8, -67, 73, -74, 79, -80, -72, -154, 238, -239, 39, -119, 163, -237, 97, -98, 310, -402, -22, -297, 336, -337, 271, -272, 20, -659, 369, -738
Offset: 0
Keywords
Links
- Ilya Gutkovskiy, Extended graphical example
Programs
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Mathematica
a[n_] := a[n] = -Sum[a[n - d], {d, Divisors[n]}]; a[0] = 1; Table[a[n], {n, 0, 65}]
Formula
a(p) = -a(p-1) - 1, for p is a prime.