A079480 a(1) = 1; a(2) = 2; a(n) = LS(a(n-1)) + LS(a(n-2)) if n > 2, where LS(m) = the "Look and Say" description (A045918) of m.
1, 2, 23, 1225, 113428, 2113253433, 1221133328272641, 112221332439252927292834, 2132112312141319233733522435243624342725, 121113122112131112111411131119124449343834282634242925352431253324352529
Offset: 1
Examples
E.g. a(7) = LS(a(6))+LS(a(5)). LS(a(6)) = LS(2113253433) = 1221131215131423, LS(a(5)) = LS(113428) = 2113141218 -> a(7) = 1221133328272641
Programs
-
Mathematica
RunLengthEncode[x_List] := (Through[{First, Length}[ #1]] &) /@ Split[x]; LS[n_] := FromDigits[ Reverse[ Flatten[ RunLengthEncode[ Reverse[ IntegerDigits[n]]]]]]; a[1] = 1; a[2] = 2; a[n_] := a[n] = LS[a[n - 1]] + LS[a[n - 2]]; Table[a[n], {n, 1, 10}]
Extensions
More terms from Mark Hudson (mrmarkhudson(AT)hotmail.com), Jan 24 2003
Corrected and edited by Robert G. Wilson v, Jan 27 2003