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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 (list; graph; refs; listen; history; text; internal format)
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, A127421-A127430.

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

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Last modified December 2 19:13 EST 2016. Contains 278683 sequences.