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A080818 Triangle read by rows in which the n-th row contains n distinct numbers whose sum is the smallest square. 3
1, 1, 3, 1, 2, 6, 1, 2, 3, 10, 1, 2, 3, 4, 6, 1, 2, 3, 4, 5, 10, 1, 2, 3, 4, 5, 6, 15, 1, 2, 3, 4, 5, 6, 7, 8, 1, 2, 3, 4, 5, 6, 7, 8, 13, 1, 2, 3, 4, 5, 6, 7, 8, 9, 19, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 26, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 15, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 22, 1, 2, 3, 4, 5, 6, 7, 8 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

If n(n+1)/2 is a square triangular number then the n-th row contains first n natural numbers (e.g., the 8th row).

LINKS

Table of n, a(n) for n=1..99.

EXAMPLE

1; 1,3; 1,2,6; 1,2,3,10; 1,2,3,4,6; 1,2,3,4,5,10; 1,2,3,4,5,6,15; 1,2,3,4,5,6,...

MAPLE

seq(op([seq(i, i=1..n-1), (ceil(sqrt(n*(n+1)/2)))^2 - n*(n-1)/2]), n=1..15); # C. Ronaldo

CROSSREFS

Cf. A080817, A080819, A080820.

Sequence in context: A112571 A051277 A300908 * A334354 A052417 A130509

Adjacent sequences:  A080815 A080816 A080817 * A080819 A080820 A080821

KEYWORD

nonn,tabl

AUTHOR

Amarnath Murthy, Mar 21 2003

EXTENSIONS

More terms from C. Ronaldo (aga_new_ac(AT)hotmail.com), Dec 19 2004

STATUS

approved

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Last modified January 27 23:41 EST 2022. Contains 350654 sequences. (Running on oeis4.)