[Guest]

1, 5, 14, 30, 55, 91, ???, ???,

whats next and why?

[Guest]

first number: 1^2

second: 2^2+previous ans (1)=5

third: 3^2+5=9+5=14

fourth: 4^2+14=16+14=30

fifth: 5^2+30=25+30=55

last given number: 6^2+55=36+55=91

first new number: 7^2+91=49+91=140

second new number: 8^2+140=64+140=204

[Guest]

first number: 1^2

second: 2^2+previous ans (1)=5

third: 3^2+5=9+5=14

fourth: 4^2+14=16+14=30

fifth: 5^2+30=25+30=55

last given number: 6^2+55=36+55=91

first new number: 7^2+91=49+91=140

second new number: 8^2+140=64+140=204

you could have left it 10 minuets,

[Guest]

you could have left it 10 minuets,

sorry... i guess i should have...

you can try my sequence

[Guest]

Yeah, liked it too

140, 204

Edited March 28, 2009 by gianfun

[Guest]

its 49+91=140

[bonanova]

This is the sequence of square pyramidal numbers:

a_n = {sum i=1,n} i²

Start with an nxn square array of spheres.

place on them an [n-1]x[n-1] square array,

and so forth up to a single sphere at the top.

The entire square pyramid will have a_n spheres.