login

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

A071440
Start with 1; add the digits of the previous term and the squares of the digits of the previous term.
2
1, 2, 6, 42, 26, 48, 92, 96, 132, 20, 6, 42, 26, 48, 92, 96, 132, 20, 6, 42, 26, 48, 92, 96, 132, 20, 6, 42, 26, 48, 92, 96, 132, 20, 6, 42, 26, 48, 92, 96, 132, 20, 6, 42, 26, 48, 92, 96, 132, 20, 6, 42, 26, 48, 92, 96, 132, 20, 6, 42, 26, 48, 92, 96, 132, 20, 6, 42, 26, 48
OFFSET
0,2
COMMENTS
The sequence becomes periodic after ten steps: a(10) = a(2). Period length is 8, length of the preperiodic part is 2. - Other starting values except 9, 90, 900, ... result in sequences which exhibit essentially the same behavior.
EXAMPLE
42 -> 4 + 2 + 4^2 + 2^2 = 26, 26 -> 2 + 6 + 2^2 + 6^2 = 48, ...
PROG
(PARI) {m=70; a=1; for(j=1, m, print1(a, ", "); n=a; a=0; while(n>0, d=divrem(n, 10); n=d[1]; a=a+(1+d[2])*d[2]))}
CROSSREFS
Sequence in context: A326268 A096138 A004153 * A371513 A280043 A309813
KEYWORD
nonn,base,easy
AUTHOR
N. J. A. Sloane, Oct 23 2002
EXTENSIONS
Edited and extended by Klaus Brockhaus, Oct 24 2002
STATUS
approved