

A135643


Straightline numbers > 99.


16



111, 123, 135, 147, 159, 210, 222, 234, 246, 258, 321, 333, 345, 357, 369, 420, 432, 444, 456, 468, 531, 543, 555, 567, 579, 630, 642, 654, 666, 678, 741, 753, 765, 777, 789, 840, 852, 864, 876, 888, 951, 963, 975, 987, 999, 1111, 1234
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OFFSET

1,1


COMMENTS

Numbers with more than two digits whose digits are in arithmetic progression. The structure of digits represent a straight line. In the graphic representation the points are connected by imaginary line segments. For a(1) to a(45) this sequence is equal to A034840. If the member of this sequence is greater than 9876543210 then the member is a repdigit number A010785.
Note that the sequence of straightline numbers starts: 10, 11, 12, ..., 98, 99, 111, 123, ... The integers with 2 digits are always straightline numbers, but here the numbers < 100 are omitted. [Omar E. Pol, Nov 14 2009]


LINKS

Jens Kruse Andersen, Table of n, a(n) for n = 1..168


EXAMPLE

The number 3579 is a straightline number:
. . . 9
. . . .
. . 7 .
. . . .
. 5 . .
. . . .
3 . . .
. . . .
. . . .
. . . .


MATHEMATICA

Select[Range[100, 1300], Length[Union[Differences[IntegerDigits[#]]]]==1&] (* Harvey P. Dale, May 09 2012 *)


PROG

(Haskell)
a135643 n = a135643_list !! (n1)
a135643_list = filter f [100..] where
f x = all (== 0) ws where
ws = zipWith () (tail vs) vs
vs = zipWith () (tail us) us
us = map (read . return) $ show x
 Reinhard Zumkeller, Sep 21 2014
(PARI) is(n) = my (d=digits(n), cvx=0, ccv=0, str=0); for (i=1, #d2, my (x=d[i]+d[i+2]2*d[i+1]); if (x>0, cvx++, x<0, ccv++, str++)); return (cvx==0 && ccv==0 && str>0) \\ Rémy Sigrist, Aug 09 2017


CROSSREFS

Cf. A010785, A034840.
Cf. A135600, A135601, A135602, A135603, A135641, A135642, A163278, A167847. [Omar E. Pol, Nov 14 2009]
Cf. A247616 (subsequence).
Sequence in context: A280636 A039990 A034840 * A070798 A235039 A279423
Adjacent sequences: A135640 A135641 A135642 * A135644 A135645 A135646


KEYWORD

nonn,base


AUTHOR

Omar E. Pol, Nov 30 2007, Dec 09 2008, Nov 14 2009


STATUS

approved



