login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A068624 a(1) = 9; a(n+1) = smallest triangular number > a(n) formed by adding at least one digit to a(n). 4
9, 91, 1891, 18915, 1989015, 199890015, 19998900015, 1999989000015, 199999890000015, 19999998900000015, 1999999989000000015, 199999999890000000015, 19999999998900000000015 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..13.

FORMULA

For n>=4, a(n) = 2*10^(2n-4) - 11*10^(n-2) + 15 [From Max Alekseyev, Apr 25 2009]

CROSSREFS

Cf. A068618, A068619, A068621, A068622, A068623.

Sequence in context: A123792 A022520 A020236 * A034666 A022505 A225162

Adjacent sequences:  A068621 A068622 A068623 * A068625 A068626 A068627

KEYWORD

base,more,nonn

AUTHOR

Amarnath Murthy, Feb 25 2002

EXTENSIONS

3 more terms from Ray G. Opao, Dec 09 2004

Extended by Max Alekseyev, Apr 25 2009

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified September 30 21:27 EDT 2020. Contains 337440 sequences. (Running on oeis4.)