

A064865


Fill a triangular array by rows by writing numbers 1, then 1 up to 2^2, then 1 up to 3^2, then 1 up to 4^2 and so on. The final elements of the rows form the sequence.


17



1, 2, 1, 5, 1, 7, 14, 6, 15, 25, 11, 23, 36, 14, 29, 45, 13, 31, 50, 6, 27, 49, 72, 15, 40, 66, 93, 21, 50, 80, 111, 22, 55, 89, 124, 16, 53, 91, 130, 1, 42, 84, 127, 171, 20, 66, 113, 161, 210, 35, 86, 138, 191, 245, 44, 100, 157, 215, 274, 45, 106, 168, 231, 295, 36
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OFFSET

1,2


COMMENTS

Does every number appear at least once? Do some numbers like 1 appear infinitely often?  Robert G. Wilson v, Oct 10 2001
Difference between nth triangular number and largest square pyramidal number (A000330) less than it.  Franklin T. AdamsWatters, Sep 11 2006


LINKS

Alois P. Heinz, Table of n, a(n) for n = 1..10000


FORMULA

a(n) = n(n+1)/2  max_{p(m) < n(n+1)/2} p(m), where p(m) = m(m+1)(2m+1)/6.  Franklin T. AdamsWatters, Sep 11 2006


EXAMPLE

The triangle begins:
....1
...1.2
..3.4.1
.2.3.4.5
6.7.8.9.1


MATHEMATICA

a = {}; Do[a = Append[a, Table[i, {i, 1, n^2} ]], {n, 1, 100} ]; a = Flatten[a]; Do[Print[a[[n(n + 1)/2]]], {n, 1, 100} ]


CROSSREFS

Table: A064866.
Cf. A000217, A000330.
Sequence in context: A263454 A036073 A124227 * A178472 A331888 A178470
Adjacent sequences: A064862 A064863 A064864 * A064866 A064867 A064868


KEYWORD

easy,nonn


AUTHOR

Floor van Lamoen, Oct 08 2001


EXTENSIONS

More terms from Robert G. Wilson v, Oct 10 2001


STATUS

approved



