OFFSET
0,2
COMMENTS
Conjecture: 101 is the largest prime term, the only other primes being 2 and 11.
The conjecture is false: for example, 181 and 383 are prime terms. There are 150 prime terms less than 75000. - Harvey P. Dale, Sep 02 2016
LINKS
Harvey P. Dale, Table of n, a(n) for n = 0..10000
FORMULA
{k + R(k)}/2 where k uses only odd digits 0, 2, 4, 6 and 8.
MAPLE
reversal := proc(n) local i, len, new, temp: new := 0: temp := n: len := floor(log[10](n+.1))+1: for i from 1 to len do new := new+irem(temp, 10)*10^(len-i): temp := floor(temp/10): od: RETURN(new): end: alleven := proc(n) local i, flag, len, temp: temp := n: flag := 1: if n=0 then flag := 0 fi: len := floor(log[10](n+.1))+1: for i from 1 to len do if irem(temp, 10) mod 2 = 0 then temp := floor(temp/10) else flag := 0 fi: od: RETURN(flag): end: for n from 0 to 500 by 2 do if alleven(n) = 1 then printf(`%d, `, (n+reversal(n))/2) fi: od: # James A. Sellers, May 28 2002
MATHEMATICA
Mean[{#, IntegerReverse[#]}]&/@(FromDigits/@Tuples[{0, 2, 4, 6, 8}, 3]) (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Sep 02 2016 *)
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Amarnath Murthy, May 20 2002
EXTENSIONS
More terms from James A. Sellers, May 28 2002
Corrected by Harvey P. Dale, Sep 02 2016
STATUS
approved