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 A213437 Nonlinear recurrence: a(n) = a(n-1) + (a(n-1)+1)*Product_{j=1..n-2} a(j). (Formerly N1082) 6
 1, 3, 7, 31, 703, 459007, 210066847231, 44127887746116242376703, 1947270476915296449559747573381594836628779007 (list; graph; refs; listen; history; text; internal format)
 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 a(n) = A001699(n)/A001699(n-1); a(n+1) - a(n) = A001699(n) + A001699(n-1); a(n) = A003095(n) + A003095(n-1). - Peter Bala, Feb 03 2017 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, a==3}, a, {n, 1, 10}] (* Vaclav Kotesovec, May 06 2015 *) PROG (PARI) a=; 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 Cf. A076949, A214635, A214636, A003095, A001699. Sequence in context: A121810 A081475 A123212 * A070231 A263049 A167917 Adjacent sequences:  A213434 A213435 A213436 * A213438 A213439 A213440 KEYWORD nonn AUTHOR N. J. A. Sloane, Jun 11 2012 EXTENSIONS Definition recovered by Johan de Ruiter, Jul 23 2012 STATUS approved

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Last modified November 30 05:31 EST 2020. Contains 338781 sequences. (Running on oeis4.)