

A240927


Positive integers with 2k digits (the first of which not 0) where the sum of the first k digits equals the sum of the last k digits.


2



11, 22, 33, 44, 55, 66, 77, 88, 99, 1001, 1010, 1102, 1111, 1120, 1203, 1212, 1221, 1230, 1304, 1313, 1322, 1331, 1340, 1405, 1414, 1423, 1432, 1441, 1450, 1506, 1515, 1524, 1533, 1542, 1551, 1560, 1607, 1616, 1625, 1634, 1643, 1652, 1661, 1670, 1708, 1717
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,1


COMMENTS

These integers are sometimes called balanced numbers.
There are 9, 615, 50412, 4379055, 392406145, ... 2kdigit balanced numbers with k >= 1.


REFERENCES

Cambridge Colleges Sixth Term Examination Papers (STEP) 2007, Paper I, Section A (Pure Mathematics), Nr. 1.


LINKS

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


EXAMPLE

1423 is a 4digit balanced number, because the sum of the first 2 digits equals the sum of the last 2 digits: 1 + 4 = 2 + 3.


CROSSREFS

Cf. A016061, A197083, A240928, A240929.
Sequence in context: A241899 A226468 A283871 * A272655 A056524 A110745
Adjacent sequences: A240924 A240925 A240926 * A240928 A240929 A240930


KEYWORD

nonn,base


AUTHOR

Martin Renner, Aug 03 2014


STATUS

approved



