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A145272 First differences of successive iterated triangular numbers. 1
1, 3, 15, 210, 26565, 358999410, 64449908117864115 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Also a triangular number -- follows from the definition of A007501.

LINKS

Table of n, a(n) for n=1..7.

FORMULA

a(n)=T(x(n-1))-x(n-1) where x(n)=T(x(n-1)) and T(x)=x*(x+1)/2.

EXAMPLE

a(1)=T(2)-2

a(2)=T(3)-3

a(3)=T(6)-6

CROSSREFS

A007501: First differences of successive terms of sequence A007501.

Sequence in context: A003505 A270354 A120601 * A264705 A117820 A126453

Adjacent sequences:  A145269 A145270 A145271 * A145273 A145274 A145275

KEYWORD

easy,nonn

AUTHOR

Greg Huber, Oct 06 2008

STATUS

approved

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Last modified August 12 21:52 EDT 2022. Contains 356077 sequences. (Running on oeis4.)