A070221 a(n)=LPF(n+1)-LPF(n), where LPF(n) denotes the largest prime factor of n.
1, -1, 3, -2, 4, -5, 1, 2, 6, -8, 10, -6, -2, -3, 15, -14, 16, -14, 2, 4, 12, -20, 2, 8, -10, 4, 22, -24, 26, -29, 9, 6, -10, -4, 34, -18, -6, -8, 36, -34, 36, -32, -6, 18, 24, -44, 4, -2, 12, -4, 40, -50, 8, -4, 12, 10, 30, -54, 56, -30, -24, -5, 11, -2, 56, -50, 6, -16, 64, -68, 70, -36, -32, 14, -8, 2, 66, -74, -2, 38, 42, -76
Offset: 2
Keywords
Examples
a(12) = LPF(13)-LPF(12) = 13 - 3 = 10.
Programs
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Mathematica
g[n_] := Module[{a, b}, a = FactorInteger[n]; b = Length[a]; a[[b]][[1]]]; f[n_] := g[n + 1] - g[n]; Table[f[i], {i, 2, 100}]