A039691 If n=x1x2...xm in base 10, n belongs to the sequence iff x1x2..xm*11=y1y2...ym and xm..x2x1*11=ym...y2y1.

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, 27, 30, 31, 32, 33, 34, 35, 36, 40, 41, 42, 43, 44, 45, 50, 51, 52, 53, 54, 60, 61, 62, 63, 70, 71, 72, 80, 81, 90, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110

Offset

1,3

Comments

This pattern works whenever the adjacent digits of a number do not add to more than 9.

A059632(a(n)) = 11*a(n). - Reinhard Zumkeller, Jul 05 2014

References

D. Wells, Curious and interesting numbers, Penguin Books, p. 156

Links

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Example

45*11=495 and 54*11=594, so 45 is a term.

Prog

(Haskell)
a039691 n = a039691_list !! (n-1)
a039691_list = filter (f 0) [0..] where
   f d x = d' + d < 10 && (x < 10 || f d' x') where (x', d') = divMod x 10
-- Reinhard Zumkeller, Jul 05 2014
(PARI) isok(n) = my(d = digits(n), y = n*11); fromdigits(Vecrev(digits(y))) == fromdigits(Vecrev(d))*11; \\ Michel Marcus, Sep 05 2017

Crossrefs

Cf. A003714, A242407.

Sequence in context: A276568 A295020 A298359 * A298639 A276347 A076121

Adjacent sequences: A039688 A039689 A039690 * A039692 A039693 A039694

Keyword

easy,base,nonn

Author

Felice Russo

Extensions

Offset corrected by Reinhard Zumkeller, Jul 05 2014

Status

approved