A100792 Group the natural numbers so that the n-th group contains n(n+1)/2 = T(n) terms: (1), (2,3,4), (5,6,7,8,9,10), (11,12,13,14,15,16,17,18,19,20),(21,22,23,24,25,26,27,28,29,30,31,32,33,34,35),... The r-th term of the n-th row of the following triangle is the sum of the next r terms of the n-th group, e.g. third row is (5),(6+7), (8+9+10) or 5,13,27. Sequence contains the triangle read by rows.

1, 2, 7, 5, 13, 27, 11, 25, 45, 74, 21, 45, 75, 114, 165, 36, 75, 120, 174, 240, 321, 57, 117, 183, 258, 345, 447, 567, 85, 173, 267, 370, 485, 615, 763, 932, 121, 245, 375, 514, 665, 831, 1015, 1220, 1449, 166, 335, 510, 694, 890, 1101, 1330, 1580, 1854, 2155

Offset

1,2

Links

Table of n, a(n) for n=1..55.

Example

1
2 7
5 13 27
11 25 45 74
21 45 75 114 165
...

Crossrefs

Cf. A100791.

Sequence in context: A294075 A165355 A038004 * A096037 A286379 A343314

Adjacent sequences: A100789 A100790 A100791 * A100793 A100794 A100795

Keyword

easy,nonn,tabl

Author

Amarnath Murthy, Dec 01 2004

Extensions

More terms from Ray Chandler, Dec 10 2004

Status

approved