

A003621


Number of iterations until n reaches 1 or 4 under x goes to sum of squares of digits map.
(Formerly M4764)


13



0, 1, 11, 0, 8, 13, 5, 9, 10, 1, 2, 9, 2, 10, 10, 7, 9, 9, 4, 1, 9, 10, 3, 2, 7, 9, 10, 3, 6, 11, 2, 3, 10, 8, 9, 12, 6, 7, 11, 8, 10, 2, 8, 4, 11, 8, 9, 10, 4, 8, 10, 7, 9, 11, 9, 8, 10, 5, 8, 13, 7, 9, 12, 8, 8, 11, 6, 2, 12, 5, 9, 10, 6, 9, 10, 6, 5, 4, 3, 9
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,3


REFERENCES

J. Roberts, Lure of the Integers, Math. Assoc. America, 1992, p. 13.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).


LINKS



FORMULA



MAPLE

f:= n > convert(map(t > t^2, convert(n, base, 10)), `+`):
g:= proc(n) option remember;
if n = 1 or n = 4 then 0 else 1 + procname(f(n)) fi
end proc:


MATHEMATICA

Table[Length[NestWhileList[Total[IntegerDigits[#]^2]&, n, #!=1&&#!=4&]], {n, 80}]1 (* Harvey P. Dale, Dec 31 2016 *)


CROSSREFS



KEYWORD

nonn,base


AUTHOR



STATUS

approved



