

A127421


Numbers whose decimal expansion is a concatenation of 2 consecutive increasing numbers.


5



1, 12, 23, 34, 45, 56, 67, 78, 89, 910, 1011, 1112, 1213, 1314, 1415, 1516, 1617, 1718, 1819, 1920, 2021, 2122, 2223, 2324, 2425, 2526, 2627, 2728, 2829, 2930, 3031, 3132, 3233, 3334, 3435, 3536, 3637, 3738, 3839, 3940, 4041, 4142, 4243, 4344, 4445, 4546
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OFFSET

1,2


COMMENTS

Primes of the sequence are in A030458. [Bruno Berselli, Mar 25 2015]


LINKS

Table of n, a(n) for n=1..46.


FORMULA

a(n)=n*10^{1+floor[log(n+1)]}+n+1, with n>=0  Paolo P. Lava, May 09 2008


EXAMPLE

a(1) = "0,1" = 1.
a(13)=1213 because 12 and 13 are two consecutive increasing numbers


MAPLE

P:=proc(n) local a, i; for i from 0 by 1 to n do a:=i*10^(1+floor(evalf(log10(i+1), 10)))+i+1; print(a); od; end: P(100);  Paolo P. Lava, May 09 2008


PROG

(MAGMA) [Seqint(Intseq(n+1) cat Intseq(n)): n in [0..50]]; // Bruno Berselli, Mar 25 2015


CROSSREFS

A variant of A001704.
Cf. A030458, A127421A127430.
Sequence in context: A072485 A035333 A001704 * A112131 A233032 A088997
Adjacent sequences: A127418 A127419 A127420 * A127422 A127423 A127424


KEYWORD

nonn,base,easy


AUTHOR

Artur Jasinski, Jan 14 2007


EXTENSIONS

More terms from Joshua Zucker, May 15 2007


STATUS

approved



