OFFSET
1,1
FORMULA
a(n) = a(n-1) + A020639(a(n-1)^2 - 1) - 1. - R. J. Mathar, May 31 2010
MAPLE
MATHEMATICA
lpf[n_] := FactorInteger[n][[1, 1]];
a[n_] := a[n] = If[n == 1, 4, a[n-1]+lpf[a[n-1]^2-1]-1];
Table[a[n], {n, 1, 50}] (* Jean-François Alcover, May 13 2023 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladimir Shevelev, May 15 2010
STATUS
approved