OFFSET
1,2
COMMENTS
This sequence was going to be included in the Aho-Sloane paper, but was omitted from the published version.
It appears that the sequence becomes periodic mod 10^k for any k, with period 3. The last digits are (1,3,7) repeated. Modulo 10^5 the sequence enters the cycle (56703, 79007, 23231) after the first 10 terms. - M. F. Hasler, Jul 23 2012. See also A214635, A214636.
REFERENCES
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
LINKS
A. V. Aho and N. J. A. Sloane, Some doubly exponential sequences, Fib. Quart., 11 (1973), 429-437. [Includes many similar sequences, although not this one.]
FORMULA
a(n) = a(n-1)+(a(n-1)+1)*(a(n-1)-a(n-2))*a(n-2)/(a(n-2)+1). - Johan de Ruiter, Jul 23 2012
a(2+3k) = 9007 (mod 10^4) for all k>0. - M. F. Hasler, Jul 23 2012
a(n) ~ c^(2^n), where c = A076949 = 1.2259024435287485386279474959130085213212293209696612823177009... . - Vaclav Kotesovec, May 06 2015
MAPLE
A213437 := proc(n)
if n = 1 then 1;
else procname(n-1)+(1+procname(n-1))*mul(procname(j), j=1..n-2);
end if;
end proc: # R. J. Mathar, Jul 23 2012
MATHEMATICA
RecurrenceTable[{a[n] == a[n-1]+(a[n-1]+1)*(a[n-1]-a[n-2])*a[n-2]/(a[n-2]+1), a[1]==1, a[2]==3}, a, {n, 1, 10}] (* Vaclav Kotesovec, May 06 2015 *)
PROG
(PARI) a=[1]; for(n=1, 11, a=concat(a, a[n] + (a[n]+1) * prod(k=1, n-1, a[k] ))); a \\ - M. F. Hasler, Jul 23 2012
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Jun 11 2012
EXTENSIONS
Definition recovered by Johan de Ruiter, Jul 23 2012
STATUS
approved