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%I #14 Sep 05 2017 08:19:07
%S 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,20,21,22,23,24,25,26,
%T 27,30,31,32,33,34,35,36,40,41,42,43,44,45,50,51,52,53,54,60,61,62,63,
%U 70,71,72,80,81,90,100,101,102,103,104,105,106,107,108,109,110
%N If n=x1x2...xm in base 10, n belongs to the sequence iff x1x2..xm*11=y1y2...ym and xm..x2x1*11=ym...y2y1.
%C This pattern works whenever the adjacent digits of a number do not add to more than 9.
%C A059632(a(n)) = 11*a(n). - _Reinhard Zumkeller_, Jul 05 2014
%D D. Wells, Curious and interesting numbers, Penguin Books, p. 156
%H Reinhard Zumkeller, <a href="/A039691/b039691.txt">Table of n, a(n) for n = 1..10000</a>
%e 45*11=495 and 54*11=594, so 45 is a term.
%o (Haskell)
%o a039691 n = a039691_list !! (n-1)
%o a039691_list = filter (f 0) [0..] where
%o f d x = d' + d < 10 && (x < 10 || f d' x') where (x', d') = divMod x 10
%o -- _Reinhard Zumkeller_, Jul 05 2014
%o (PARI) isok(n) = my(d = digits(n), y = n*11); fromdigits(Vecrev(digits(y))) == fromdigits(Vecrev(d))*11; \\ _Michel Marcus_, Sep 05 2017
%Y Cf. A003714, A242407.
%K easy,base,nonn
%O 1,3
%A _Felice Russo_
%E Offset corrected by _Reinhard Zumkeller_, Jul 05 2014
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