The OEIS mourns the passing of Jim Simons and is grateful to the Simons Foundation for its support of research in many branches of science, including the OEIS.
The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A269632 a(1)=1. At any step consider the terms as two streams of digits: the first read from left to right and the second from right to left. Sum the two numbers and add them as new term of the sequence. Repeat. 1
 1, 2, 33, 4554, 57877875, 7021243003421196, 81446984612990832809030548964517, 8388153908186958083116465238561550559414647202908596818094507838 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Paolo P. Lava, Table of n, a(n) for n = 1..11 FORMULA Sum_{k >= 1} a(k)/a(k+1) = 0.567931128577306235186022447895934719336343085... a(n) == 0 (mod 9), for n>3. - Ivan N. Ianakiev, Mar 08 2016 EXAMPLE First step: 1; the two numbers are obviously 1 and 1 which sum to 2; sequence becomes 1, 2. Second step: 1, 2; the two numbers are 12 and 21 that sum to 33; sequence becomes 1, 2, 33. Third step: 1, 2, 33: the two numbers are 1233 and 3321 that sum to 4554; sequence becomes 1, 2, 33, 4554; etc. MAPLE P:=proc(q) local a, b, c, d, k, n; a:=[1]; print(1); for n from 1 to q do b:=a[1]; for k from 2 to nops(a) do b:=10*b+a[k]; od; c:=a[nops(a)]; for k from nops(a)-1 by -1 to 1 do c:=10*c+a[k]; od; d:=b+c; print(d); for k from 1 to ilog10(d)+1 do a:=[op(a), (trunc(d/10^(ilog10(d)+1-k)) mod 10)]; od; od; print(); end: P(15); MATHEMATICA a = {1}; Do[AppendTo[a, FromDigits@ # + FromDigits@ Reverse@ # &@ Flatten@ Map[IntegerDigits, a]], {n, 2, 9}]; a (* Michael De Vlieger, Mar 03 2016 *) CROSSREFS Sequence in context: A302452 A113105 A132567 * A083459 A368899 A034173 Adjacent sequences: A269629 A269630 A269631 * A269633 A269634 A269635 KEYWORD nonn,base,easy AUTHOR Paolo P. Lava, Mar 02 2016 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified June 15 03:12 EDT 2024. Contains 373402 sequences. (Running on oeis4.)